Boston Marathon bombing: Dramatic images of manhunt, suspect in custody

A daylong manhunt culminated Friday evening with authorities taking suspected Boston Marathon bomber Dzhokhar Tsarnaev, 19, into custody alive. Tsarnaev was found hiding on a boat in the yard of a Franklin Street home in the Boston suburb of Watertown.

Y! News: Complete coverage of Boston Marathon bombing | Man gave police tip about boat | Suspects' aunt: 'This was staged'

ALTERNATE CROP - This still frame from video shows Boston Marathon bombing suspect Dzhokhar Tsarnaev visible through an ambulance after he was captured in Watertown, Mass., Friday, April 19, 2013.A 19-year-old college student wanted in the Boston Marathon bombings was taken into custody Friday evening after a manhunt that left the city virtually paralyzed and his older brother and accomplice dead. (AP Photo/Robert Ray)
ALTERNATE CROP - This still frame from video shows Boston Marathon bombing suspect Dzhokhar Tsarnaev visible through an ambulance after he was captured in Watertown, Mass., Friday, April 19, 2013.A 19-year-old college student wanted in the Boston Marathon bombings was taken into custody Friday evening after a manhunt that left the city virtually paralyzed and his older brother and accomplice dead. (AP Photo/Robert Ray)
ALTERNATE CROP - This still frame from video shows Boston Marathon bombing suspect Dzhokhar Tsarnaev visible through an ambulance after he was captured in Watertown, Mass., Friday, April 19, 2013.A 19-year-old college student wanted in the Boston Marathon bombings was taken into custody Friday evening after a manhunt that left the city virtually paralyzed and his older brother and accomplice dead. (AP Photo/Robert Ray)
Police officers guard the entrance to Franklin street where there is an active crime scene search for the suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. Gunfire erupted Friday night amid the manhunt for the surviving suspect in the Boston Marathon bombing, and police in armored vehicles and tactical gear rushed into the Watertown neighborhood in a possible break in the case. (AP Photo/Matt Rourke)
Police officers guard the entrance to Franklin street where there is an active crime scene search for the suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. Gunfire erupted Friday night amid the manhunt for the surviving suspect in the Boston Marathon bombing, and police in armored vehicles and tactical gear rushed into the Watertown neighborhood in a possible break in the case. (AP Photo/Matt Rourke)
Police officers guard the entrance to Franklin street where there is an active crime scene search for the suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. Gunfire erupted Friday night amid the manhunt for the surviving suspect in the Boston Marathon bombing, and police in armored vehicles and tactical gear rushed into the Watertown neighborhood in a possible break in the case. (AP Photo/Matt Rourke)
Mimi de Quesada, of Watertown, Mass., reacts while standing by her home in the wake of the sound of shots fired in Watertown, Mass., Friday, April 19, 2013, as a massive search continued for one of two suspects in the Boston Marathon bombings. De Quesada said she had just come out to enjoy the day when the shots rang out about two blocks form her home. A second suspect died in the early morning hours after an encounter with law enforcement. (AP Photo/Craig Ruttle)
Mimi de Quesada, of Watertown, Mass., reacts while standing by her home in the wake of the sound of shots fired in Watertown, Mass., Friday, April 19, 2013, as a massive search continued for one of two suspects in the Boston Marathon bombings. De Quesada said she had just come out to enjoy the day when the shots rang out about two blocks form her home. A second suspect died in the early morning hours after an encounter with law enforcement. (AP Photo/Craig Ruttle)
Mimi de Quesada, of Watertown, Mass., reacts while standing by her home in the wake of the sound of shots fired in Watertown, Mass., Friday, April 19, 2013, as a massive search continued for one of two suspects in the Boston Marathon bombings. De Quesada said she had just come out to enjoy the day when the shots rang out about two blocks form her home. A second suspect died in the early morning hours after an encounter with law enforcement. (AP Photo/Craig Ruttle)
Heavily armed police officers do house to house searches in the neighborhoods of Watertown, Mass. Friday, April 19, 2013, as a massive search continued for one of two suspects in the Boston Marathon bombing. A second suspect died in the early morning hours after an encounter with law enforcement. (AP Photo/Craig Ruttle)
Heavily armed police officers do house to house searches in the neighborhoods of Watertown, Mass. Friday, April 19, 2013, as a massive search continued for one of two suspects in the Boston Marathon bombing. A second suspect died in the early morning hours after an encounter with law enforcement. (AP Photo/Craig Ruttle)
Heavily armed police officers do house to house searches in the neighborhoods of Watertown, Mass. Friday, April 19, 2013, as a massive search continued for one of two suspects in the Boston Marathon bombing. A second suspect died in the early morning hours after an encounter with law enforcement. (AP Photo/Craig Ruttle)
People watch as police search for suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. Gunfire erupted Friday night amid the manhunt for the surviving suspect in the Boston Marathon bombing, and police in armored vehicles and tactical gear rushed into the Watertown neighborhood in a possible break in the case. (AP Photo/Matt Rourke)
People watch as police search for suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. Gunfire erupted Friday night amid the manhunt for the surviving suspect in the Boston Marathon bombing, and police in armored vehicles and tactical gear rushed into the Watertown neighborhood in a possible break in the case. (AP Photo/Matt Rourke)
People watch as police search for suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. Gunfire erupted Friday night amid the manhunt for the surviving suspect in the Boston Marathon bombing, and police in armored vehicles and tactical gear rushed into the Watertown neighborhood in a possible break in the case. (AP Photo/Matt Rourke)
Law enforcement search for the suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. Gunfire erupted Friday night amid the manhunt for the surviving suspect in the Boston Marathon bombing, and police in armored vehicles and tactical gear rushed into the Watertown neighborhood in a possible break in the case. (AP Photo/Matt Rourke)
Law enforcement search for the suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. Gunfire erupted Friday night amid the manhunt for the surviving suspect in the Boston Marathon bombing, and police in armored vehicles and tactical gear rushed into the Watertown neighborhood in a possible break in the case. (AP Photo/Matt Rourke)
Law enforcement search for the suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. Gunfire erupted Friday night amid the manhunt for the surviving suspect in the Boston Marathon bombing, and police in armored vehicles and tactical gear rushed into the Watertown neighborhood in a possible break in the case. (AP Photo/Matt Rourke)
This combination of photos provided on Friday, April 19, 2013 by the Federal Bureau of Investigation, left, and the Boston Regional Intelligence Center, right, shows a suspect that officials have identified as Dzhokhar Tsarnaev, being sought by police in connection with Monday's Boston Marathon bombings. (AP Photo/FBI, BRIC)
This combination of photos provided on Friday, April 19, 2013 by the Federal Bureau of Investigation, left, and the Boston Regional Intelligence Center, right, shows a suspect that officials have identified as Dzhokhar Tsarnaev, being sought by police in connection with Monday's Boston Marathon bombings. (AP Photo/FBI, BRIC)
This combination of photos provided on Friday, April 19, 2013 by the Federal Bureau of Investigation, left, and the Boston Regional Intelligence Center, right, shows a suspect that officials have identified as Dzhokhar Tsarnaev, being sought by police in connection with Monday's Boston Marathon bombings. (AP Photo/FBI, BRIC)
Officials wearing tactical gear stand near an armored vehicle as they search an apartment building for one of two suspects in the Boston Marathon bombing, in Watertown, Mass., Friday, April 19, 2013. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during a getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Julio Cortez)
Officials wearing tactical gear stand near an armored vehicle as they search an apartment building for one of two suspects in the Boston Marathon bombing, in Watertown, Mass., Friday, April 19, 2013. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during a getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Julio Cortez)
Officials wearing tactical gear stand near an armored vehicle as they search an apartment building for one of two suspects in the Boston Marathon bombing, in Watertown, Mass., Friday, April 19, 2013. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during a getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Julio Cortez)
The usually busy Kenmore Square in Boston is virtually deserted at lunchtime Friday, April 19, 2013, during a call for "shelter-in-place" for Boston and some area communities. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during their getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Elise Amendola)
The usually busy Kenmore Square in Boston is virtually deserted at lunchtime Friday, April 19, 2013, during a call for "shelter-in-place" for Boston and some area communities. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during their getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Elise Amendola)
The usually busy Kenmore Square in Boston is virtually deserted at lunchtime Friday, April 19, 2013, during a call for "shelter-in-place" for Boston and some area communities. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during their getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Elise Amendola)
A police officer evacuates a shoeless man holding a child as members of law enforcement conduct a search for a suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. The two suspects in the Boston Marathon bombing killed an MIT police officer and hurled explosives at police in a car chase and gun battle overnight that left one of them dead and his brother on the loose, authorities said Friday as thousands of officers swarmed the streets in a manhunt that all but paralyzed the Boston area. (AP Photo/Matt Rourke)
A police officer evacuates a shoeless man holding a child as members of law enforcement conduct a search for a suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. The two suspects in the Boston Marathon bombing killed an MIT police officer and hurled explosives at police in a car chase and gun battle overnight that left one of them dead and his brother on the loose, authorities said Friday as thousands of officers swarmed the streets in a manhunt that all but paralyzed the Boston area. (AP Photo/Matt Rourke)
A police officer evacuates a shoeless man holding a child as members of law enforcement conduct a search for a suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. The two suspects in the Boston Marathon bombing killed an MIT police officer and hurled explosives at police in a car chase and gun battle overnight that left one of them dead and his brother on the loose, authorities said Friday as thousands of officers swarmed the streets in a manhunt that all but paralyzed the Boston area. (AP Photo/Matt Rourke)
This undated photo provided by the Middlesex District Attorney's Office shows Massachusetts Institute of Technology Police Officer Sean Collier, 26, of Somerville, Mass., who was shot to death Thursday, April 18, 2013 on the school campus in Cambridge, Mass. Authorities said surveillance tape recorded late Thursday showed one of the Boston Marathon bombing suspects during a robbery of a nearby convenience store before Collier was shot to death while responding to a report of a disturbance. (AP Photo/Middlesex District Attorney's Office)
This undated photo provided by the Middlesex District Attorney's Office shows Massachusetts Institute of Technology Police Officer Sean Collier, 26, of Somerville, Mass., who was shot to death Thursday, April 18, 2013 on the school campus in Cambridge, Mass. Authorities said surveillance tape recorded late Thursday showed one of the Boston Marathon bombing suspects during a robbery of a nearby convenience store before Collier was shot to death while responding to a report of a disturbance. (AP Photo/Middlesex District Attorney's Office)
This undated photo provided by the Middlesex District Attorney's Office shows Massachusetts Institute of Technology Police Officer Sean Collier, 26, of Somerville, Mass., who was shot to death Thursday, April 18, 2013 on the school campus in Cambridge, Mass. Authorities said surveillance tape recorded late Thursday showed one of the Boston Marathon bombing suspects during a robbery of a nearby convenience store before Collier was shot to death while responding to a report of a disturbance. (AP Photo/Middlesex District Attorney's Office)
This undated photo provided by the Massachusetts Bay Transportation Authority shows transit police officer Richard Donohue, 33, who was critically injured in an early morning shootout Friday, April 19, 2013, with the two suspects in the Boston Marathon bombings. (AP Photo/Massachusetts Bay Transportation Authority)
This undated photo provided by the Massachusetts Bay Transportation Authority shows transit police officer Richard Donohue, 33, who was critically injured in an early morning shootout Friday, April 19, 2013, with the two suspects in the Boston Marathon bombings. (AP Photo/Massachusetts Bay Transportation Authority)
This undated photo provided by the Massachusetts Bay Transportation Authority shows transit police officer Richard Donohue, 33, who was critically injured in an early morning shootout Friday, April 19, 2013, with the two suspects in the Boston Marathon bombings. (AP Photo/Massachusetts Bay Transportation Authority)
A sign along I-93 in Medford, Mass. announces no MBTA service Friday, April 19, 2013. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during their getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Elise Amendola)
A sign along I-93 in Medford, Mass. announces no MBTA service Friday, April 19, 2013. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during their getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Elise Amendola)
A sign along I-93 in Medford, Mass. announces no MBTA service Friday, April 19, 2013. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during their getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Elise Amendola)
The Amtrak departures board shows a canceled train to Boston at Penn Station, Friday, April 19, 2013 in New York. Mass transit to and from the Boston area was virtually shut down Friday as police conducted a massive manhunt for a suspect in Monday's Boston Marathon bombing. (AP Photo/Jason DeCrow)
The Amtrak departures board shows a canceled train to Boston at Penn Station, Friday, April 19, 2013 in New York. Mass transit to and from the Boston area was virtually shut down Friday as police conducted a massive manhunt for a suspect in Monday's Boston Marathon bombing. (AP Photo/Jason DeCrow)
The Amtrak departures board shows a canceled train to Boston at Penn Station, Friday, April 19, 2013 in New York. Mass transit to and from the Boston area was virtually shut down Friday as police conducted a massive manhunt for a suspect in Monday's Boston Marathon bombing. (AP Photo/Jason DeCrow)
Heavily armed police officers do house to house searches in the neighborhoods of Watertown, Mass. Friday, April 19, 2013, as a massive search continued for one of two suspects in the Boston Marathon bombing. A second suspect died in the early morning hours after an encounter with law enforcement. (AP Photo/Craig Ruttle)
Heavily armed police officers do house to house searches in the neighborhoods of Watertown, Mass. Friday, April 19, 2013, as a massive search continued for one of two suspects in the Boston Marathon bombing. A second suspect died in the early morning hours after an encounter with law enforcement. (AP Photo/Craig Ruttle)
Heavily armed police officers do house to house searches in the neighborhoods of Watertown, Mass. Friday, April 19, 2013, as a massive search continued for one of two suspects in the Boston Marathon bombing. A second suspect died in the early morning hours after an encounter with law enforcement. (AP Photo/Craig Ruttle)
People watch as police search for suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. Gunfire erupted Friday night amid the manhunt for the surviving suspect in the Boston Marathon bombing, and police in armored vehicles and tactical gear rushed into the Watertown neighborhood in a possible break in the case. (AP Photo/Matt Rourke)
People watch as police search for suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. Gunfire erupted Friday night amid the manhunt for the surviving suspect in the Boston Marathon bombing, and police in armored vehicles and tactical gear rushed into the Watertown neighborhood in a possible break in the case. (AP Photo/Matt Rourke)
People watch as police search for suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. Gunfire erupted Friday night amid the manhunt for the surviving suspect in the Boston Marathon bombing, and police in armored vehicles and tactical gear rushed into the Watertown neighborhood in a possible break in the case. (AP Photo/Matt Rourke)
Law enforcement search for the suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. Gunfire erupted Friday night amid the manhunt for the surviving suspect in the Boston Marathon bombing, and police in armored vehicles and tactical gear rushed into the Watertown neighborhood in a possible break in the case. (AP Photo/Matt Rourke)
Law enforcement search for the suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. Gunfire erupted Friday night amid the manhunt for the surviving suspect in the Boston Marathon bombing, and police in armored vehicles and tactical gear rushed into the Watertown neighborhood in a possible break in the case. (AP Photo/Matt Rourke)
Law enforcement search for the suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. Gunfire erupted Friday night amid the manhunt for the surviving suspect in the Boston Marathon bombing, and police in armored vehicles and tactical gear rushed into the Watertown neighborhood in a possible break in the case. (AP Photo/Matt Rourke)
This combination of photos provided on Friday, April 19, 2013 by the Federal Bureau of Investigation, left, and the Boston Regional Intelligence Center, right, shows a suspect that officials have identified as Dzhokhar Tsarnaev, being sought by police in connection with Monday's Boston Marathon bombings. (AP Photo/FBI, BRIC)
This combination of photos provided on Friday, April 19, 2013 by the Federal Bureau of Investigation, left, and the Boston Regional Intelligence Center, right, shows a suspect that officials have identified as Dzhokhar Tsarnaev, being sought by police in connection with Monday's Boston Marathon bombings. (AP Photo/FBI, BRIC)
This combination of photos provided on Friday, April 19, 2013 by the Federal Bureau of Investigation, left, and the Boston Regional Intelligence Center, right, shows a suspect that officials have identified as Dzhokhar Tsarnaev, being sought by police in connection with Monday's Boston Marathon bombings. (AP Photo/FBI, BRIC)
Officials wearing tactical gear stand near an armored vehicle as they search an apartment building for one of two suspects in the Boston Marathon bombing, in Watertown, Mass., Friday, April 19, 2013. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during a getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Julio Cortez)
Officials wearing tactical gear stand near an armored vehicle as they search an apartment building for one of two suspects in the Boston Marathon bombing, in Watertown, Mass., Friday, April 19, 2013. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during a getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Julio Cortez)
Officials wearing tactical gear stand near an armored vehicle as they search an apartment building for one of two suspects in the Boston Marathon bombing, in Watertown, Mass., Friday, April 19, 2013. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during a getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Julio Cortez)
The usually busy Kenmore Square in Boston is virtually deserted at lunchtime Friday, April 19, 2013, during a call for "shelter-in-place" for Boston and some area communities. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during their getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Elise Amendola)
The usually busy Kenmore Square in Boston is virtually deserted at lunchtime Friday, April 19, 2013, during a call for "shelter-in-place" for Boston and some area communities. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during their getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Elise Amendola)
The usually busy Kenmore Square in Boston is virtually deserted at lunchtime Friday, April 19, 2013, during a call for "shelter-in-place" for Boston and some area communities. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during their getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Elise Amendola)
A police officer evacuates a shoeless man holding a child as members of law enforcement conduct a search for a suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. The two suspects in the Boston Marathon bombing killed an MIT police officer and hurled explosives at police in a car chase and gun battle overnight that left one of them dead and his brother on the loose, authorities said Friday as thousands of officers swarmed the streets in a manhunt that all but paralyzed the Boston area. (AP Photo/Matt Rourke)
A police officer evacuates a shoeless man holding a child as members of law enforcement conduct a search for a suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. The two suspects in the Boston Marathon bombing killed an MIT police officer and hurled explosives at police in a car chase and gun battle overnight that left one of them dead and his brother on the loose, authorities said Friday as thousands of officers swarmed the streets in a manhunt that all but paralyzed the Boston area. (AP Photo/Matt Rourke)
A police officer evacuates a shoeless man holding a child as members of law enforcement conduct a search for a suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. The two suspects in the Boston Marathon bombing killed an MIT police officer and hurled explosives at police in a car chase and gun battle overnight that left one of them dead and his brother on the loose, authorities said Friday as thousands of officers swarmed the streets in a manhunt that all but paralyzed the Boston area. (AP Photo/Matt Rourke)
This undated photo provided by the Middlesex District Attorney's Office shows Massachusetts Institute of Technology Police Officer Sean Collier, 26, of Somerville, Mass., who was shot to death Thursday, April 18, 2013 on the school campus in Cambridge, Mass. Authorities said surveillance tape recorded late Thursday showed one of the Boston Marathon bombing suspects during a robbery of a nearby convenience store before Collier was shot to death while responding to a report of a disturbance. (AP Photo/Middlesex District Attorney's Office)
This undated photo provided by the Middlesex District Attorney's Office shows Massachusetts Institute of Technology Police Officer Sean Collier, 26, of Somerville, Mass., who was shot to death Thursday, April 18, 2013 on the school campus in Cambridge, Mass. Authorities said surveillance tape recorded late Thursday showed one of the Boston Marathon bombing suspects during a robbery of a nearby convenience store before Collier was shot to death while responding to a report of a disturbance. (AP Photo/Middlesex District Attorney's Office)
This undated photo provided by the Middlesex District Attorney's Office shows Massachusetts Institute of Technology Police Officer Sean Collier, 26, of Somerville, Mass., who was shot to death Thursday, April 18, 2013 on the school campus in Cambridge, Mass. Authorities said surveillance tape recorded late Thursday showed one of the Boston Marathon bombing suspects during a robbery of a nearby convenience store before Collier was shot to death while responding to a report of a disturbance. (AP Photo/Middlesex District Attorney's Office)
This undated photo provided by the Massachusetts Bay Transportation Authority shows transit police officer Richard Donohue, 33, who was critically injured in an early morning shootout Friday, April 19, 2013, with the two suspects in the Boston Marathon bombings. (AP Photo/Massachusetts Bay Transportation Authority)
This undated photo provided by the Massachusetts Bay Transportation Authority shows transit police officer Richard Donohue, 33, who was critically injured in an early morning shootout Friday, April 19, 2013, with the two suspects in the Boston Marathon bombings. (AP Photo/Massachusetts Bay Transportation Authority)
This undated photo provided by the Massachusetts Bay Transportation Authority shows transit police officer Richard Donohue, 33, who was critically injured in an early morning shootout Friday, April 19, 2013, with the two suspects in the Boston Marathon bombings. (AP Photo/Massachusetts Bay Transportation Authority)
A sign along I-93 in Medford, Mass. announces no MBTA service Friday, April 19, 2013. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during their getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Elise Amendola)
A sign along I-93 in Medford, Mass. announces no MBTA service Friday, April 19, 2013. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during their getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Elise Amendola)
A sign along I-93 in Medford, Mass. announces no MBTA service Friday, April 19, 2013. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during their getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Elise Amendola)
The Amtrak departures board shows a canceled train to Boston at Penn Station, Friday, April 19, 2013 in New York. Mass transit to and from the Boston area was virtually shut down Friday as police conducted a massive manhunt for a suspect in Monday's Boston Marathon bombing. (AP Photo/Jason DeCrow)
The Amtrak departures board shows a canceled train to Boston at Penn Station, Friday, April 19, 2013 in New York. Mass transit to and from the Boston area was virtually shut down Friday as police conducted a massive manhunt for a suspect in Monday's Boston Marathon bombing. (AP Photo/Jason DeCrow)
The Amtrak departures board shows a canceled train to Boston at Penn Station, Friday, April 19, 2013 in New York. Mass transit to and from the Boston area was virtually shut down Friday as police conducted a massive manhunt for a suspect in Monday's Boston Marathon bombing. (AP Photo/Jason DeCrow)
Officials wearing tactical gear stand near an armored vehicle as they search an apartment building for one of two suspects in the Boston Marathon bombing, in Watertown, Mass., Friday, April 19, 2013. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during a getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Julio Cortez)
Officials wearing tactical gear stand near an armored vehicle as they search an apartment building for one of two suspects in the Boston Marathon bombing, in Watertown, Mass., Friday, April 19, 2013. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during a getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Julio Cortez)
Officials wearing tactical gear stand near an armored vehicle as they search an apartment building for one of two suspects in the Boston Marathon bombing, in Watertown, Mass., Friday, April 19, 2013. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during a getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Julio Cortez)
The usually busy Kenmore Square in Boston is virtually deserted at lunchtime Friday, April 19, 2013, during a call for "shelter-in-place" for Boston and some area communities. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during their getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Elise Amendola)
The usually busy Kenmore Square in Boston is virtually deserted at lunchtime Friday, April 19, 2013, during a call for "shelter-in-place" for Boston and some area communities. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during their getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Elise Amendola)
The usually busy Kenmore Square in Boston is virtually deserted at lunchtime Friday, April 19, 2013, during a call for "shelter-in-place" for Boston and some area communities. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during their getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Elise Amendola)
A police officer evacuates a shoeless man holding a child as members of law enforcement conduct a search for a suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. The two suspects in the Boston Marathon bombing killed an MIT police officer and hurled explosives at police in a car chase and gun battle overnight that left one of them dead and his brother on the loose, authorities said Friday as thousands of officers swarmed the streets in a manhunt that all but paralyzed the Boston area. (AP Photo/Matt Rourke)
A police officer evacuates a shoeless man holding a child as members of law enforcement conduct a search for a suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. The two suspects in the Boston Marathon bombing killed an MIT police officer and hurled explosives at police in a car chase and gun battle overnight that left one of them dead and his brother on the loose, authorities said Friday as thousands of officers swarmed the streets in a manhunt that all but paralyzed the Boston area. (AP Photo/Matt Rourke)
A police officer evacuates a shoeless man holding a child as members of law enforcement conduct a search for a suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. The two suspects in the Boston Marathon bombing killed an MIT police officer and hurled explosives at police in a car chase and gun battle overnight that left one of them dead and his brother on the loose, authorities said Friday as thousands of officers swarmed the streets in a manhunt that all but paralyzed the Boston area. (AP Photo/Matt Rourke)
This undated photo provided by the Middlesex District Attorney's Office shows Massachusetts Institute of Technology Police Officer Sean Collier, 26, of Somerville, Mass., who was shot to death Thursday, April 18, 2013 on the school campus in Cambridge, Mass. Authorities said surveillance tape recorded late Thursday showed one of the Boston Marathon bombing suspects during a robbery of a nearby convenience store before Collier was shot to death while responding to a report of a disturbance. (AP Photo/Middlesex District Attorney's Office)
This undated photo provided by the Middlesex District Attorney's Office shows Massachusetts Institute of Technology Police Officer Sean Collier, 26, of Somerville, Mass., who was shot to death Thursday, April 18, 2013 on the school campus in Cambridge, Mass. Authorities said surveillance tape recorded late Thursday showed one of the Boston Marathon bombing suspects during a robbery of a nearby convenience store before Collier was shot to death while responding to a report of a disturbance. (AP Photo/Middlesex District Attorney's Office)
This undated photo provided by the Middlesex District Attorney's Office shows Massachusetts Institute of Technology Police Officer Sean Collier, 26, of Somerville, Mass., who was shot to death Thursday, April 18, 2013 on the school campus in Cambridge, Mass. Authorities said surveillance tape recorded late Thursday showed one of the Boston Marathon bombing suspects during a robbery of a nearby convenience store before Collier was shot to death while responding to a report of a disturbance. (AP Photo/Middlesex District Attorney's Office)
This undated photo provided by the Massachusetts Bay Transportation Authority shows transit police officer Richard Donohue, 33, who was critically injured in an early morning shootout Friday, April 19, 2013, with the two suspects in the Boston Marathon bombings. (AP Photo/Massachusetts Bay Transportation Authority)
This undated photo provided by the Massachusetts Bay Transportation Authority shows transit police officer Richard Donohue, 33, who was critically injured in an early morning shootout Friday, April 19, 2013, with the two suspects in the Boston Marathon bombings. (AP Photo/Massachusetts Bay Transportation Authority)
This undated photo provided by the Massachusetts Bay Transportation Authority shows transit police officer Richard Donohue, 33, who was critically injured in an early morning shootout Friday, April 19, 2013, with the two suspects in the Boston Marathon bombings. (AP Photo/Massachusetts Bay Transportation Authority)
A sign along I-93 in Medford, Mass. announces no MBTA service Friday, April 19, 2013. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during their getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Elise Amendola)
A sign along I-93 in Medford, Mass. announces no MBTA service Friday, April 19, 2013. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during their getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Elise Amendola)
A sign along I-93 in Medford, Mass. announces no MBTA service Friday, April 19, 2013. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during their getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Elise Amendola)
The Amtrak departures board shows a canceled train to Boston at Penn Station, Friday, April 19, 2013 in New York. Mass transit to and from the Boston area was virtually shut down Friday as police conducted a massive manhunt for a suspect in Monday's Boston Marathon bombing. (AP Photo/Jason DeCrow)
The Amtrak departures board shows a canceled train to Boston at Penn Station, Friday, April 19, 2013 in New York. Mass transit to and from the Boston area was virtually shut down Friday as police conducted a massive manhunt for a suspect in Monday's Boston Marathon bombing. (AP Photo/Jason DeCrow)
The Amtrak departures board shows a canceled train to Boston at Penn Station, Friday, April 19, 2013 in New York. Mass transit to and from the Boston area was virtually shut down Friday as police conducted a massive manhunt for a suspect in Monday's Boston Marathon bombing. (AP Photo/Jason DeCrow)
Commuters are turned away at Malden Center station in Malden, Mass. Friday, April 19, 2013 as area MBTA commuter trains are suspended. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during a getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Elise Amendola)
Commuters are turned away at Malden Center station in Malden, Mass. Friday, April 19, 2013 as area MBTA commuter trains are suspended. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during a getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Elise Amendola)
Commuters are turned away at Malden Center station in Malden, Mass. Friday, April 19, 2013 as area MBTA commuter trains are suspended. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during a getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Elise Amendola)
Police in tactical gear conduct a search for a suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. The bombs that blew up seconds apart near the finish line of the Boston Marathon left the streets spattered with blood and glass, and gaping questions of who chose to attack and why. (AP Photo/Matt Rourke)
Police in tactical gear conduct a search for a suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. The bombs that blew up seconds apart near the finish line of the Boston Marathon left the streets spattered with blood and glass, and gaping questions of who chose to attack and why. (AP Photo/Matt Rourke)
Police in tactical gear conduct a search for a suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. The bombs that blew up seconds apart near the finish line of the Boston Marathon left the streets spattered with blood and glass, and gaping questions of who chose to attack and why. (AP Photo/Matt Rourke)
A barefooted woman runs for cover as police surround a home while searching for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during a getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Charles Krupa)
A barefooted woman runs for cover as police surround a home while searching for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during a getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Charles Krupa)
A barefooted woman runs for cover as police surround a home while searching for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during a getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Charles Krupa)
A neighbor is escorted to safety as police surround a home while searching for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. The two suspects in the Boston Marathon bombing killed an MIT police officer and hurled explosives at police in a car chase and gun battle overnight that left one of them dead and his brother on the loose, authorities said Friday. (AP Photo/Charles Krupa)
A neighbor is escorted to safety as police surround a home while searching for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. The two suspects in the Boston Marathon bombing killed an MIT police officer and hurled explosives at police in a car chase and gun battle overnight that left one of them dead and his brother on the loose, authorities said Friday. (AP Photo/Charles Krupa)
A neighbor is escorted to safety as police surround a home while searching for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. The two suspects in the Boston Marathon bombing killed an MIT police officer and hurled explosives at police in a car chase and gun battle overnight that left one of them dead and his brother on the loose, authorities said Friday. (AP Photo/Charles Krupa)
A police officer with is weapon drawn conducts a search for a suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. The two suspects in the Boston Marathon bombing killed an MIT police officer and hurled explosives at police in a car chase and gun battle overnight that left one of them dead and his brother on the loose, authorities said Friday as thousands of officers swarmed the streets in a manhunt that all but paralyzed the Boston area. (AP Photo/Matt Rourke)
A police officer with is weapon drawn conducts a search for a suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. The two suspects in the Boston Marathon bombing killed an MIT police officer and hurled explosives at police in a car chase and gun battle overnight that left one of them dead and his brother on the loose, authorities said Friday as thousands of officers swarmed the streets in a manhunt that all but paralyzed the Boston area. (AP Photo/Matt Rourke)
A police officer with is weapon drawn conducts a search for a suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. The two suspects in the Boston Marathon bombing killed an MIT police officer and hurled explosives at police in a car chase and gun battle overnight that left one of them dead and his brother on the loose, authorities said Friday as thousands of officers swarmed the streets in a manhunt that all but paralyzed the Boston area. (AP Photo/Matt Rourke)
The Amtrak departures board shows a canceled train to Boston at Penn Station, Friday, April 19, 2013 in New York. Mass transit to and from the Boston area was virtually shut down Friday as police conducted a massive manhunt for a suspect in Monday's Boston Marathon bombing. (AP Photo/Jason DeCrow)
The Amtrak departures board shows a canceled train to Boston at Penn Station, Friday, April 19, 2013 in New York. Mass transit to and from the Boston area was virtually shut down Friday as police conducted a massive manhunt for a suspect in Monday's Boston Marathon bombing. (AP Photo/Jason DeCrow)
The Amtrak departures board shows a canceled train to Boston at Penn Station, Friday, April 19, 2013 in New York. Mass transit to and from the Boston area was virtually shut down Friday as police conducted a massive manhunt for a suspect in Monday's Boston Marathon bombing. (AP Photo/Jason DeCrow)
Commuters are turned away at Malden Center station in Malden, Mass. Friday, April 19, 2013 as area MBTA commuter trains are suspended. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during a getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Elise Amendola)
Commuters are turned away at Malden Center station in Malden, Mass. Friday, April 19, 2013 as area MBTA commuter trains are suspended. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during a getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Elise Amendola)
Commuters are turned away at Malden Center station in Malden, Mass. Friday, April 19, 2013 as area MBTA commuter trains are suspended. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during a getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Elise Amendola)
Police in tactical gear conduct a search for a suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. The bombs that blew up seconds apart near the finish line of the Boston Marathon left the streets spattered with blood and glass, and gaping questions of who chose to attack and why. (AP Photo/Matt Rourke)
Police in tactical gear conduct a search for a suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. The bombs that blew up seconds apart near the finish line of the Boston Marathon left the streets spattered with blood and glass, and gaping questions of who chose to attack and why. (AP Photo/Matt Rourke)
Police in tactical gear conduct a search for a suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. The bombs that blew up seconds apart near the finish line of the Boston Marathon left the streets spattered with blood and glass, and gaping questions of who chose to attack and why. (AP Photo/Matt Rourke)
A barefooted woman runs for cover as police surround a home while searching for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during a getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Charles Krupa)
A barefooted woman runs for cover as police surround a home while searching for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during a getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Charles Krupa)
A barefooted woman runs for cover as police surround a home while searching for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during a getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Charles Krupa)
A neighbor is escorted to safety as police surround a home while searching for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. The two suspects in the Boston Marathon bombing killed an MIT police officer and hurled explosives at police in a car chase and gun battle overnight that left one of them dead and his brother on the loose, authorities said Friday. (AP Photo/Charles Krupa)
A neighbor is escorted to safety as police surround a home while searching for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. The two suspects in the Boston Marathon bombing killed an MIT police officer and hurled explosives at police in a car chase and gun battle overnight that left one of them dead and his brother on the loose, authorities said Friday. (AP Photo/Charles Krupa)
A neighbor is escorted to safety as police surround a home while searching for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. The two suspects in the Boston Marathon bombing killed an MIT police officer and hurled explosives at police in a car chase and gun battle overnight that left one of them dead and his brother on the loose, authorities said Friday. (AP Photo/Charles Krupa)
A police officer with is weapon drawn conducts a search for a suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. The two suspects in the Boston Marathon bombing killed an MIT police officer and hurled explosives at police in a car chase and gun battle overnight that left one of them dead and his brother on the loose, authorities said Friday as thousands of officers swarmed the streets in a manhunt that all but paralyzed the Boston area. (AP Photo/Matt Rourke)
A police officer with is weapon drawn conducts a search for a suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. The two suspects in the Boston Marathon bombing killed an MIT police officer and hurled explosives at police in a car chase and gun battle overnight that left one of them dead and his brother on the loose, authorities said Friday as thousands of officers swarmed the streets in a manhunt that all but paralyzed the Boston area. (AP Photo/Matt Rourke)
A police officer with is weapon drawn conducts a search for a suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. The two suspects in the Boston Marathon bombing killed an MIT police officer and hurled explosives at police in a car chase and gun battle overnight that left one of them dead and his brother on the loose, authorities said Friday as thousands of officers swarmed the streets in a manhunt that all but paralyzed the Boston area. (AP Photo/Matt Rourke)
Maret Tsarnaeva, an aunt of the two suspects in the Boston Marathon bombing, holds a reporter's smart phone which displays a scene from the bomb site, as she speaks to journalists in the lobby of her apartment building in Toronto on Friday April 19, 2013. Tamerlan Tsarnaev, a 26-year-old who had been known to the FBI as Suspect No. 1 and was seen in surveillance footage in a black baseball cap, was killed overnight, officials said. His brother, a 19-year-old college student who was dubbed Suspect No. 2 and was seen wearing a white, backward baseball cap in the images from Monday's deadly bombing at the marathon finish line, escaped. (AP Photo/The Canadian Press, Chris Young)
Maret Tsarnaeva, an aunt of the two suspects in the Boston Marathon bombing, holds a reporter's smart phone which displays a scene from the bomb site, as she speaks to journalists in the lobby of her apartment building in Toronto on Friday April 19, 2013. Tamerlan Tsarnaev, a 26-year-old who had been known to the FBI as Suspect No. 1 and was seen in surveillance footage in a black baseball cap, was killed overnight, officials said. His brother, a 19-year-old college student who was dubbed Suspect No. 2 and was seen wearing a white, backward baseball cap in the images from Monday's deadly bombing at the marathon finish line, escaped. (AP Photo/The Canadian Press, Chris Young)
Maret Tsarnaeva, an aunt of the two suspects in the Boston Marathon bombing, holds a reporter's smart phone which displays a scene from the bomb site, as she speaks to journalists in the lobby of her apartment building in Toronto on Friday April 19, 2013. Tamerlan Tsarnaev, a 26-year-old who had been known to the FBI as Suspect No. 1 and was seen in surveillance footage in a black baseball cap, was killed overnight, officials said. His brother, a 19-year-old college student who was dubbed Suspect No. 2 and was seen wearing a white, backward baseball cap in the images from Monday's deadly bombing at the marathon finish line, escaped. (AP Photo/The Canadian Press, Chris Young)
In this photo provided by Harold Cobin, traffic is halted and an Amtrak Acela train sits on the track in Norwalk, Conn., Friday, April 19, 2013, after Norwalk police were asked by Boston police to search the train for Dzhokhar Tsarnaev, the the remaining Boston Marathon bombings suspect. An Amtrak spokesman said the southbound train was allowed to continue to Washington about 9:30 a.m. Amtrak suspended service between Boston and Providence, R.I., about 5:45 a.m., Friday at the request of Massachusetts authorities. (AP Photo/Harold Cobin)
In this photo provided by Harold Cobin, traffic is halted and an Amtrak Acela train sits on the track in Norwalk, Conn., Friday, April 19, 2013, after Norwalk police were asked by Boston police to search the train for Dzhokhar Tsarnaev, the the remaining Boston Marathon bombings suspect. An Amtrak spokesman said the southbound train was allowed to continue to Washington about 9:30 a.m. Amtrak suspended service between Boston and Providence, R.I., about 5:45 a.m., Friday at the request of Massachusetts authorities. (AP Photo/Harold Cobin)
In this photo provided by Harold Cobin, traffic is halted and an Amtrak Acela train sits on the track in Norwalk, Conn., Friday, April 19, 2013, after Norwalk police were asked by Boston police to search the train for Dzhokhar Tsarnaev, the the remaining Boston Marathon bombings suspect. An Amtrak spokesman said the southbound train was allowed to continue to Washington about 9:30 a.m. Amtrak suspended service between Boston and Providence, R.I., about 5:45 a.m., Friday at the request of Massachusetts authorities. (AP Photo/Harold Cobin)
Ruslan Tsarni, the uncle of the Boston Marathon bombing suspect, speaks with the media outside his home in Montgomery Village in Md. Friday, April, 19, 2013. Tsarni urged his nephew to turn himself in. (AP Photo/Jose Luis Magana)
Ruslan Tsarni, the uncle of the Boston Marathon bombing suspect, speaks with the media outside his home in Montgomery Village in Md. Friday, April, 19, 2013. Tsarni urged his nephew to turn himself in. (AP Photo/Jose Luis Magana)
Ruslan Tsarni, the uncle of the Boston Marathon bombing suspect, speaks with the media outside his home in Montgomery Village in Md. Friday, April, 19, 2013. Tsarni urged his nephew to turn himself in. (AP Photo/Jose Luis Magana)
�8BOSTON - APRIL 19: At around 9:30 a.m., Friend Street near North Station was empty, as all public transportation was suspended. There is a Lockdown-in-Place in effect in Boston as the manhunt for the second suspect in the Boston Marathon bombings continues. (Photo by Jim Davis/The Boston Globe via Getty Images)
boston manhunt
8BOSTON - APRIL 19: At around 9:30 a.m., Friend Street near North Station was empty, as all public transportation was suspended. There is a Lockdown-in-Place in effect in Boston as the manhunt for the second suspect in the Boston Marathon bombings continues. (Photo by Jim Davis/The Boston Globe via Getty Images)
�àBOSTON, MA - APRIL 19: A swat team member scouts the perimeter of South Station on April 19, 2013 in Boston, Massachusetts. South Station was shut down and heavily guarded with police in response to the early morning shootings in Cambridge and Watertown, Massachusetts. After a car chase and shoot out with police, one suspect in the Boston Marathon bombing, Tamerlan Tsarnaev, 26, was shot and killed by police early morning April 19, and a manhunt is underway for his brother and second suspect, 19-year-old suspect Dzhokhar A. Tsarnaev. The two men, reportedly Chechen origin, are suspects in the bombings at the Boston Marathon on April 15, that killed three people and wounded at least 170. (Photo by Kayana Szymczak/Getty Images)
boston manhu
àBOSTON, MA - APRIL 19: A swat team member scouts the perimeter of South Station on April 19, 2013 in Boston, Massachusetts. South Station was shut down and heavily guarded with police in response to the early morning shootings in Cambridge and Watertown, Massachusetts. After a car chase and shoot out with police, one suspect in the Boston Marathon bombing, Tamerlan Tsarnaev, 26, was shot and killed by police early morning April 19, and a manhunt is underway for his brother and second suspect, 19-year-old suspect Dzhokhar A. Tsarnaev. The two men, reportedly Chechen origin, are suspects in the bombings at the Boston Marathon on April 15, that killed three people and wounded at least 170. (Photo by Kayana Szymczak/Getty Images)
�'CAMBRIDGE, MA - APRIL 19: The Boston area is under lockdown as as a manhunt is underway for a suspect in the terrorist bombing of the 117th Boston Marathon earlier this week. The Mass. Avenue bridge has only a few pedestrians crossing. (Photo by Jonathan Wiggs/The Boston Globe via Getty Images)
boston manhunt
'CAMBRIDGE, MA - APRIL 19: The Boston area is under lockdown as as a manhunt is underway for a suspect in the terrorist bombing of the 117th Boston Marathon earlier this week. The Mass. Avenue bridge has only a few pedestrians crossing. (Photo by Jonathan Wiggs/The Boston Globe via Getty Images)
Maret Tsarnaeva, an aunt of the two suspects in the Boston Marathon bombing, holds a reporter's smart phone which displays a scene from the bomb site, as she speaks to journalists in the lobby of her apartment building in Toronto on Friday April 19, 2013. Tamerlan Tsarnaev, a 26-year-old who had been known to the FBI as Suspect No. 1 and was seen in surveillance footage in a black baseball cap, was killed overnight, officials said. His brother, a 19-year-old college student who was dubbed Suspect No. 2 and was seen wearing a white, backward baseball cap in the images from Monday's deadly bombing at the marathon finish line, escaped. (AP Photo/The Canadian Press, Chris Young)
Maret Tsarnaeva, an aunt of the two suspects in the Boston Marathon bombing, holds a reporter's smart phone which displays a scene from the bomb site, as she speaks to journalists in the lobby of her apartment building in Toronto on Friday April 19, 2013. Tamerlan Tsarnaev, a 26-year-old who had been known to the FBI as Suspect No. 1 and was seen in surveillance footage in a black baseball cap, was killed overnight, officials said. His brother, a 19-year-old college student who was dubbed Suspect No. 2 and was seen wearing a white, backward baseball cap in the images from Monday's deadly bombing at the marathon finish line, escaped. (AP Photo/The Canadian Press, Chris Young)
Maret Tsarnaeva, an aunt of the two suspects in the Boston Marathon bombing, holds a reporter's smart phone which displays a scene from the bomb site, as she speaks to journalists in the lobby of her apartment building in Toronto on Friday April 19, 2013. Tamerlan Tsarnaev, a 26-year-old who had been known to the FBI as Suspect No. 1 and was seen in surveillance footage in a black baseball cap, was killed overnight, officials said. His brother, a 19-year-old college student who was dubbed Suspect No. 2 and was seen wearing a white, backward baseball cap in the images from Monday's deadly bombing at the marathon finish line, escaped. (AP Photo/The Canadian Press, Chris Young)
In this photo provided by Harold Cobin, traffic is halted and an Amtrak Acela train sits on the track in Norwalk, Conn., Friday, April 19, 2013, after Norwalk police were asked by Boston police to search the train for Dzhokhar Tsarnaev, the the remaining Boston Marathon bombings suspect. An Amtrak spokesman said the southbound train was allowed to continue to Washington about 9:30 a.m. Amtrak suspended service between Boston and Providence, R.I., about 5:45 a.m., Friday at the request of Massachusetts authorities. (AP Photo/Harold Cobin)
In this photo provided by Harold Cobin, traffic is halted and an Amtrak Acela train sits on the track in Norwalk, Conn., Friday, April 19, 2013, after Norwalk police were asked by Boston police to search the train for Dzhokhar Tsarnaev, the the remaining Boston Marathon bombings suspect. An Amtrak spokesman said the southbound train was allowed to continue to Washington about 9:30 a.m. Amtrak suspended service between Boston and Providence, R.I., about 5:45 a.m., Friday at the request of Massachusetts authorities. (AP Photo/Harold Cobin)
In this photo provided by Harold Cobin, traffic is halted and an Amtrak Acela train sits on the track in Norwalk, Conn., Friday, April 19, 2013, after Norwalk police were asked by Boston police to search the train for Dzhokhar Tsarnaev, the the remaining Boston Marathon bombings suspect. An Amtrak spokesman said the southbound train was allowed to continue to Washington about 9:30 a.m. Amtrak suspended service between Boston and Providence, R.I., about 5:45 a.m., Friday at the request of Massachusetts authorities. (AP Photo/Harold Cobin)
Ruslan Tsarni, the uncle of the Boston Marathon bombing suspect, speaks with the media outside his home in Montgomery Village in Md. Friday, April, 19, 2013. Tsarni urged his nephew to turn himself in. (AP Photo/Jose Luis Magana)
Ruslan Tsarni, the uncle of the Boston Marathon bombing suspect, speaks with the media outside his home in Montgomery Village in Md. Friday, April, 19, 2013. Tsarni urged his nephew to turn himself in. (AP Photo/Jose Luis Magana)
Ruslan Tsarni, the uncle of the Boston Marathon bombing suspect, speaks with the media outside his home in Montgomery Village in Md. Friday, April, 19, 2013. Tsarni urged his nephew to turn himself in. (AP Photo/Jose Luis Magana)
�8BOSTON - APRIL 19: At around 9:30 a.m., Friend Street near North Station was empty, as all public transportation was suspended. There is a Lockdown-in-Place in effect in Boston as the manhunt for the second suspect in the Boston Marathon bombings continues. (Photo by Jim Davis/The Boston Globe via Getty Images)
boston manhunt
8BOSTON - APRIL 19: At around 9:30 a.m., Friend Street near North Station was empty, as all public transportation was suspended. There is a Lockdown-in-Place in effect in Boston as the manhunt for the second suspect in the Boston Marathon bombings continues. (Photo by Jim Davis/The Boston Globe via Getty Images)
�àBOSTON, MA - APRIL 19: A swat team member scouts the perimeter of South Station on April 19, 2013 in Boston, Massachusetts. South Station was shut down and heavily guarded with police in response to the early morning shootings in Cambridge and Watertown, Massachusetts. After a car chase and shoot out with police, one suspect in the Boston Marathon bombing, Tamerlan Tsarnaev, 26, was shot and killed by police early morning April 19, and a manhunt is underway for his brother and second suspect, 19-year-old suspect Dzhokhar A. Tsarnaev. The two men, reportedly Chechen origin, are suspects in the bombings at the Boston Marathon on April 15, that killed three people and wounded at least 170. (Photo by Kayana Szymczak/Getty Images)
boston manhu
àBOSTON, MA - APRIL 19: A swat team member scouts the perimeter of South Station on April 19, 2013 in Boston, Massachusetts. South Station was shut down and heavily guarded with police in response to the early morning shootings in Cambridge and Watertown, Massachusetts. After a car chase and shoot out with police, one suspect in the Boston Marathon bombing, Tamerlan Tsarnaev, 26, was shot and killed by police early morning April 19, and a manhunt is underway for his brother and second suspect, 19-year-old suspect Dzhokhar A. Tsarnaev. The two men, reportedly Chechen origin, are suspects in the bombings at the Boston Marathon on April 15, that killed three people and wounded at least 170. (Photo by Kayana Szymczak/Getty Images)
�'CAMBRIDGE, MA - APRIL 19: The Boston area is under lockdown as as a manhunt is underway for a suspect in the terrorist bombing of the 117th Boston Marathon earlier this week. The Mass. Avenue bridge has only a few pedestrians crossing. (Photo by Jonathan Wiggs/The Boston Globe via Getty Images)
boston manhunt
'CAMBRIDGE, MA - APRIL 19: The Boston area is under lockdown as as a manhunt is underway for a suspect in the terrorist bombing of the 117th Boston Marathon earlier this week. The Mass. Avenue bridge has only a few pedestrians crossing. (Photo by Jonathan Wiggs/The Boston Globe via Getty Images)
A Department of Homeland Security officer, right, prepares to enter an apartment building while looking for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. The bombs that blew up seconds apart near the finish line of the Boston Marathon left the streets spattered with blood and glass, and gaping questions of who chose to attack and why. (AP Photo/Charles Krupa)
A Department of Homeland Security officer, right, prepares to enter an apartment building while looking for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. The bombs that blew up seconds apart near the finish line of the Boston Marathon left the streets spattered with blood and glass, and gaping questions of who chose to attack and why. (AP Photo/Charles Krupa)
A Department of Homeland Security officer, right, prepares to enter an apartment building while looking for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. The bombs that blew up seconds apart near the finish line of the Boston Marathon left the streets spattered with blood and glass, and gaping questions of who chose to attack and why. (AP Photo/Charles Krupa)
This surveillance photo released via Twitter Friday, April 19, 2013 by the Boston Police Department shows a suspect entering a convenience store that police are pursuing in Watertown, Mass. Police say he is one of two suspects in the fatal shooting of an MIT police officer and tied to the Boston Marathon bombing. (AP Photo/Boston Police Department)
This surveillance photo released via Twitter Friday, April 19, 2013 by the Boston Police Department shows a suspect entering a convenience store that police are pursuing in Watertown, Mass. Police say he is one of two suspects in the fatal shooting of an MIT police officer and tied to the Boston Marathon bombing. (AP Photo/Boston Police Department)
This surveillance photo released via Twitter Friday, April 19, 2013 by the Boston Police Department shows a suspect entering a convenience store that police are pursuing in Watertown, Mass. Police say he is one of two suspects in the fatal shooting of an MIT police officer and tied to the Boston Marathon bombing. (AP Photo/Boston Police Department)
Police in tactical gear arrive on an armored police vehicle as they surround an apartment building while looking for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. The bombs that blew up seconds apart near the finish line of the Boston Marathon left the streets spattered with blood and glass, and gaping questions of who chose to attack and why. (AP Photo/Charles Krupa)
Police in tactical gear arrive on an armored police vehicle as they surround an apartment building while looking for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. The bombs that blew up seconds apart near the finish line of the Boston Marathon left the streets spattered with blood and glass, and gaping questions of who chose to attack and why. (AP Photo/Charles Krupa)
Police in tactical gear arrive on an armored police vehicle as they surround an apartment building while looking for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. The bombs that blew up seconds apart near the finish line of the Boston Marathon left the streets spattered with blood and glass, and gaping questions of who chose to attack and why. (AP Photo/Charles Krupa)
Police in tactical gear surround an apartment building while looking for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. The bombs that blew up seconds apart near the finish line of the Boston Marathon left the streets spattered with blood and glass, and gaping questions of who chose to attack and why. (AP Photo/Charles Krupa)
Police in tactical gear surround an apartment building while looking for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. The bombs that blew up seconds apart near the finish line of the Boston Marathon left the streets spattered with blood and glass, and gaping questions of who chose to attack and why. (AP Photo/Charles Krupa)
Police in tactical gear surround an apartment building while looking for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. The bombs that blew up seconds apart near the finish line of the Boston Marathon left the streets spattered with blood and glass, and gaping questions of who chose to attack and why. (AP Photo/Charles Krupa)
Police work a crime scene Friday, April 19, 2013, in Watertown, Mass. A tense night of police activity that left a university officer dead on campus just days after the Boston Marathon bombings and amid a hunt for two suspects caused officers to converge on a neighborhood outside Boston, where residents heard gunfire and explosions.(AP Photo/Matt Rourke)
Police work a crime scene Friday, April 19, 2013, in Watertown, Mass. A tense night of police activity that left a university officer dead on campus just days after the Boston Marathon bombings and amid a hunt for two suspects caused officers to converge on a neighborhood outside Boston, where residents heard gunfire and explosions.(AP Photo/Matt Rourke)
Police work a crime scene Friday, April 19, 2013, in Watertown, Mass. A tense night of police activity that left a university officer dead on campus just days after the Boston Marathon bombings and amid a hunt for two suspects caused officers to converge on a neighborhood outside Boston, where residents heard gunfire and explosions.(AP Photo/Matt Rourke)
A woman looks out a window at her home as police start to search an apartment building while looking for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during their getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Charles Krupa)
A woman looks out a window at her home as police start to search an apartment building while looking for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during their getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Charles Krupa)
A woman looks out a window at her home as police start to search an apartment building while looking for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during their getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Charles Krupa)
WATERTOWN, MA - APRIL 19: A police officer runs with his gun drawn while searching for a suspect on April 19, 2013 in Watertown, Massachusetts. Earlier, a Massachusetts Institute of Technology campus police officer was shot and killed late Thursday night at the school's campus in Cambridge. A short time later, police reported exchanging gunfire with alleged carjackers in Watertown, a city near Cambridge. According to reports, one suspect has been killed during a car chase and the police are seeking another - believed to be the same person wanted in connection with the deadly bombing at the Boston Marathon earlier this week. (Photo by Mario Tama/Getty Images)
Shootings In Cambridge, Watertown Draw Massive Police Response
WATERTOWN, MA - APRIL 19: A police officer runs with his gun drawn while searching for a suspect on April 19, 2013 in Watertown, Massachusetts. Earlier, a Massachusetts Institute of Technology campus police officer was shot and killed late Thursday night at the school's campus in Cambridge. A short time later, police reported exchanging gunfire with alleged carjackers in Watertown, a city near Cambridge. According to reports, one suspect has been killed during a car chase and the police are seeking another - believed to be the same person wanted in connection with the deadly bombing at the Boston Marathon earlier this week. (Photo by Mario Tama/Getty Images)
This photo released by the FBI early Friday April 19, 2013, shows what the FBI is calling the suspects together, walking through the crowd in Boston on Monday, April 15, 2013, before the explosions at the Boston Marathon. (AP Photo/FBI)
This photo released by the FBI early Friday April 19, 2013, shows what the FBI is calling the suspects together, walking through the crowd in Boston on Monday, April 15, 2013, before the explosions at the Boston Marathon. (AP Photo/FBI)
This photo released by the FBI early Friday April 19, 2013, shows what the FBI is calling the suspects together, walking through the crowd in Boston on Monday, April 15, 2013, before the explosions at the Boston Marathon. (AP Photo/FBI)
Police officers walk near a crime scene Friday, April 19, 2013, in Watertown, Mass. A tense night of police activity that left a university officer dead on campus just days after the Boston Marathon bombings and amid a hunt for two suspects caused officers to converge on a neighborhood outside Boston, where residents heard gunfire and explosions.(AP Photo/Matt Rourke)
Police officers walk near a crime scene Friday, April 19, 2013, in Watertown, Mass. A tense night of police activity that left a university officer dead on campus just days after the Boston Marathon bombings and amid a hunt for two suspects caused officers to converge on a neighborhood outside Boston, where residents heard gunfire and explosions.(AP Photo/Matt Rourke)
Police officers walk near a crime scene Friday, April 19, 2013, in Watertown, Mass. A tense night of police activity that left a university officer dead on campus just days after the Boston Marathon bombings and amid a hunt for two suspects caused officers to converge on a neighborhood outside Boston, where residents heard gunfire and explosions.(AP Photo/Matt Rourke)
This surveillance photo released via Twitter Friday, April 19, 2013 by the Boston Police Department shows a suspect entering a convenience store that police are pursuing in Watertown, Mass. Police say he is one of two suspects in the fatal shooting of an MIT police officer and tied to the Boston Marathon bombing. (AP Photo/Boston Police Department)
This surveillance photo released via Twitter Friday, April 19, 2013 by the Boston Police Department shows a suspect entering a convenience store that police are pursuing in Watertown, Mass. Police say he is one of two suspects in the fatal shooting of an MIT police officer and tied to the Boston Marathon bombing. (AP Photo/Boston Police Department)
This surveillance photo released via Twitter Friday, April 19, 2013 by the Boston Police Department shows a suspect entering a convenience store that police are pursuing in Watertown, Mass. Police say he is one of two suspects in the fatal shooting of an MIT police officer and tied to the Boston Marathon bombing. (AP Photo/Boston Police Department)
Police in tactical gear arrive on an armored police vehicle as they surround an apartment building while looking for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. The bombs that blew up seconds apart near the finish line of the Boston Marathon left the streets spattered with blood and glass, and gaping questions of who chose to attack and why. (AP Photo/Charles Krupa)
Police in tactical gear arrive on an armored police vehicle as they surround an apartment building while looking for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. The bombs that blew up seconds apart near the finish line of the Boston Marathon left the streets spattered with blood and glass, and gaping questions of who chose to attack and why. (AP Photo/Charles Krupa)
Police in tactical gear arrive on an armored police vehicle as they surround an apartment building while looking for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. The bombs that blew up seconds apart near the finish line of the Boston Marathon left the streets spattered with blood and glass, and gaping questions of who chose to attack and why. (AP Photo/Charles Krupa)
Police in tactical gear surround an apartment building while looking for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. The bombs that blew up seconds apart near the finish line of the Boston Marathon left the streets spattered with blood and glass, and gaping questions of who chose to attack and why. (AP Photo/Charles Krupa)
Police in tactical gear surround an apartment building while looking for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. The bombs that blew up seconds apart near the finish line of the Boston Marathon left the streets spattered with blood and glass, and gaping questions of who chose to attack and why. (AP Photo/Charles Krupa)
Police in tactical gear surround an apartment building while looking for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. The bombs that blew up seconds apart near the finish line of the Boston Marathon left the streets spattered with blood and glass, and gaping questions of who chose to attack and why. (AP Photo/Charles Krupa)
Police work a crime scene Friday, April 19, 2013, in Watertown, Mass. A tense night of police activity that left a university officer dead on campus just days after the Boston Marathon bombings and amid a hunt for two suspects caused officers to converge on a neighborhood outside Boston, where residents heard gunfire and explosions.(AP Photo/Matt Rourke)
Police work a crime scene Friday, April 19, 2013, in Watertown, Mass. A tense night of police activity that left a university officer dead on campus just days after the Boston Marathon bombings and amid a hunt for two suspects caused officers to converge on a neighborhood outside Boston, where residents heard gunfire and explosions.(AP Photo/Matt Rourke)
Police work a crime scene Friday, April 19, 2013, in Watertown, Mass. A tense night of police activity that left a university officer dead on campus just days after the Boston Marathon bombings and amid a hunt for two suspects caused officers to converge on a neighborhood outside Boston, where residents heard gunfire and explosions.(AP Photo/Matt Rourke)
A woman looks out a window at her home as police start to search an apartment building while looking for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during their getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Charles Krupa)
A woman looks out a window at her home as police start to search an apartment building while looking for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during their getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Charles Krupa)
A woman looks out a window at her home as police start to search an apartment building while looking for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during their getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Charles Krupa)
WATERTOWN, MA - APRIL 19: A police officer runs with his gun drawn while searching for a suspect on April 19, 2013 in Watertown, Massachusetts. Earlier, a Massachusetts Institute of Technology campus police officer was shot and killed late Thursday night at the school's campus in Cambridge. A short time later, police reported exchanging gunfire with alleged carjackers in Watertown, a city near Cambridge. According to reports, one suspect has been killed during a car chase and the police are seeking another - believed to be the same person wanted in connection with the deadly bombing at the Boston Marathon earlier this week. (Photo by Mario Tama/Getty Images)
Shootings In Cambridge, Watertown Draw Massive Police Response
WATERTOWN, MA - APRIL 19: A police officer runs with his gun drawn while searching for a suspect on April 19, 2013 in Watertown, Massachusetts. Earlier, a Massachusetts Institute of Technology campus police officer was shot and killed late Thursday night at the school's campus in Cambridge. A short time later, police reported exchanging gunfire with alleged carjackers in Watertown, a city near Cambridge. According to reports, one suspect has been killed during a car chase and the police are seeking another - believed to be the same person wanted in connection with the deadly bombing at the Boston Marathon earlier this week. (Photo by Mario Tama/Getty Images)
This photo released by the FBI early Friday April 19, 2013, shows what the FBI is calling the suspects together, walking through the crowd in Boston on Monday, April 15, 2013, before the explosions at the Boston Marathon. (AP Photo/FBI)
This photo released by the FBI early Friday April 19, 2013, shows what the FBI is calling the suspects together, walking through the crowd in Boston on Monday, April 15, 2013, before the explosions at the Boston Marathon. (AP Photo/FBI)
This photo released by the FBI early Friday April 19, 2013, shows what the FBI is calling the suspects together, walking through the crowd in Boston on Monday, April 15, 2013, before the explosions at the Boston Marathon. (AP Photo/FBI)
Police officers walk near a crime scene Friday, April 19, 2013, in Watertown, Mass. A tense night of police activity that left a university officer dead on campus just days after the Boston Marathon bombings and amid a hunt for two suspects caused officers to converge on a neighborhood outside Boston, where residents heard gunfire and explosions.(AP Photo/Matt Rourke)
Police officers walk near a crime scene Friday, April 19, 2013, in Watertown, Mass. A tense night of police activity that left a university officer dead on campus just days after the Boston Marathon bombings and amid a hunt for two suspects caused officers to converge on a neighborhood outside Boston, where residents heard gunfire and explosions.(AP Photo/Matt Rourke)
Police officers walk near a crime scene Friday, April 19, 2013, in Watertown, Mass. A tense night of police activity that left a university officer dead on campus just days after the Boston Marathon bombings and amid a hunt for two suspects caused officers to converge on a neighborhood outside Boston, where residents heard gunfire and explosions.(AP Photo/Matt Rourke)
WATERTOWN, MA - APRIL 19: Boston Police gather in the parking lot in front of a Best Buy store, near the Watertown Mall on April 19, 2013 in Watertown, Massachusetts. Earlier, a Massachusetts Institute of Technology campus police officer was shot and killed late Thursday night at the school's campus in Cambridge. A short time later, police reported exchanging gunfire with alleged carjackers in Watertown, a city near Cambridge. It's not clear whether the shootings are related or whether either are related to the Boston Marathon bombing. (Photo by Jared Wickerham/Getty Images)
Shootings In Cambridge, Watertown Draw Massive Police Response
WATERTOWN, MA - APRIL 19: Boston Police gather in the parking lot in front of a Best Buy store, near the Watertown Mall on April 19, 2013 in Watertown, Massachusetts. Earlier, a Massachusetts Institute of Technology campus police officer was shot and killed late Thursday night at the school's campus in Cambridge. A short time later, police reported exchanging gunfire with alleged carjackers in Watertown, a city near Cambridge. It's not clear whether the shootings are related or whether either are related to the Boston Marathon bombing. (Photo by Jared Wickerham/Getty Images)
WATERTOWN - APRIL 19: Police descend on School and Walnut streets in search of suspects April 19, 2013 in Watertown, Massachusetts. Earlier, a Massachusetts Institute of Technology campus police officer was shot and killed late Thursday night at the school's campus in Cambridge. A short time later, police reported exchanging gunfire with alleged carjackers in Watertown, a city near Cambridge. It's not clear whether the shootings are related or whether either are related to the Boston Marathon bombing. (Photo by Darren McCollester/Getty Images)
Shootings In Cambridge, Watertown Draw Massive Police Response
WATERTOWN - APRIL 19: Police descend on School and Walnut streets in search of suspects April 19, 2013 in Watertown, Massachusetts. Earlier, a Massachusetts Institute of Technology campus police officer was shot and killed late Thursday night at the school's campus in Cambridge. A short time later, police reported exchanging gunfire with alleged carjackers in Watertown, a city near Cambridge. It's not clear whether the shootings are related or whether either are related to the Boston Marathon bombing. (Photo by Darren McCollester/Getty Images)
Police officers aim their weapons Friday, April 19, 2013, in Watertown, Mass. A tense night of police activity that left a university officer dead on campus just days after the Boston Marathon bombings and amid a hunt for two suspects caused officers to converge on a neighborhood outside Boston, where residents heard gunfire and explosions.(AP Photo/Matt Rourke)
Police officers aim their weapons Friday, April 19, 2013, in Watertown, Mass. A tense night of police activity that left a university officer dead on campus just days after the Boston Marathon bombings and amid a hunt for two suspects caused officers to converge on a neighborhood outside Boston, where residents heard gunfire and explosions.(AP Photo/Matt Rourke)
Police officers aim their weapons Friday, April 19, 2013, in Watertown, Mass. A tense night of police activity that left a university officer dead on campus just days after the Boston Marathon bombings and amid a hunt for two suspects caused officers to converge on a neighborhood outside Boston, where residents heard gunfire and explosions.(AP Photo/Matt Rourke)
WATERTOWN, MA - APRIL 19: A police officer with gun drawn searches for a suspect on April 19, 2013 in Watertown, Massachusetts. Earlier, a Massachusetts Institute of Technology campus police officer was shot and killed late Thursday night at the school's campus in Cambridge. A short time later, police reported exchanging gunfire with alleged carjackers in Watertown, a city near Cambridge. It's not clear whether the shootings are related or whether either are related to the Boston Marathon bombing. (Photo by Mario Tama/Getty Images)
MIT Police Officer Shot On College Campus
WATERTOWN, MA - APRIL 19: A police officer with gun drawn searches for a suspect on April 19, 2013 in Watertown, Massachusetts. Earlier, a Massachusetts Institute of Technology campus police officer was shot and killed late Thursday night at the school's campus in Cambridge. A short time later, police reported exchanging gunfire with alleged carjackers in Watertown, a city near Cambridge. It's not clear whether the shootings are related or whether either are related to the Boston Marathon bombing. (Photo by Mario Tama/Getty Images)
WATERTOWN, MA - APRIL 19: Police with guns drawn search for a suspect on April 19, 2013 in Watertown, Massachusetts. Earlier, a Massachusetts Institute of Technology campus police officer was shot and killed late Thursday night at the school's campus in Cambridge. A short time later, police reported exchanging gunfire with alleged carjackers in Watertown, a city near Cambridge. It's not clear whether the shootings are related or whether either are related to the Boston Marathon bombing. (Photo by Mario Tama/Getty Images)
Shootings In Cambridge, Watertown Draw Massive Police Response
WATERTOWN, MA - APRIL 19: Police with guns drawn search for a suspect on April 19, 2013 in Watertown, Massachusetts. Earlier, a Massachusetts Institute of Technology campus police officer was shot and killed late Thursday night at the school's campus in Cambridge. A short time later, police reported exchanging gunfire with alleged carjackers in Watertown, a city near Cambridge. It's not clear whether the shootings are related or whether either are related to the Boston Marathon bombing. (Photo by Mario Tama/Getty Images)
Police officers aim their weapons Friday, April 19, 2013, in Watertown, Mass. A tense night of police activity that left a university officer dead on campus just days after the Boston Marathon bombings and amid a hunt for two suspects caused officers to converge on a neighborhood outside Boston, where residents heard gunfire and explosions.(AP Photo/Matt Rourke)
Police officers aim their weapons Friday, April 19, 2013, in Watertown, Mass. A tense night of police activity that left a university officer dead on campus just days after the Boston Marathon bombings and amid a hunt for two suspects caused officers to converge on a neighborhood outside Boston, where residents heard gunfire and explosions.(AP Photo/Matt Rourke)
Police officers aim their weapons Friday, April 19, 2013, in Watertown, Mass. A tense night of police activity that left a university officer dead on campus just days after the Boston Marathon bombings and amid a hunt for two suspects caused officers to converge on a neighborhood outside Boston, where residents heard gunfire and explosions.(AP Photo/Matt Rourke)
A vehicle carrying officers in tactical gear arrives at the Watertown neighborhood of Boston, Friday, April 19, 2013. Reports of explosives being detonated and police are telling reporters to turn off their cell phones. Dozens of officers and National Guard members are in Watertown, where television outlets report that gunfire and explosions have been heard. (AP Photo/Julio Cortez)
A vehicle carrying officers in tactical gear arrives at the Watertown neighborhood of Boston, Friday, April 19, 2013. Reports of explosives being detonated and police are telling reporters to turn off their cell phones. Dozens of officers and National Guard members are in Watertown, where television outlets report that gunfire and explosions have been heard. (AP Photo/Julio Cortez)
A vehicle carrying officers in tactical gear arrives at the Watertown neighborhood of Boston, Friday, April 19, 2013. Reports of explosives being detonated and police are telling reporters to turn off their cell phones. Dozens of officers and National Guard members are in Watertown, where television outlets report that gunfire and explosions have been heard. (AP Photo/Julio Cortez)
WATERTOWN, MA - APRIL 19: A police officer lifts police tape for a police car to pass under on April 19, 2013 in Watertown, Massachusetts. Earlier, a Massachusetts Institute of Technology campus police officer was shot and killed late Thursday night at the school's campus in Cambridge. A short time later, police reported exchanging gunfire with alleged carjackers in Watertown, a city near Cambridge. According to reports, one suspect has been killed during a car chase and the police are seeking another - believed to be the same person (known as Suspect Two) wanted in connection with the deadly bombing at the Boston Marathon earlier this week. (Photo by Mario Tama/Getty Images)
Shootings In Cambridge, Watertown Draw Massive Police Response
WATERTOWN, MA - APRIL 19: A police officer lifts police tape for a police car to pass under on April 19, 2013 in Watertown, Massachusetts. Earlier, a Massachusetts Institute of Technology campus police officer was shot and killed late Thursday night at the school's campus in Cambridge. A short time later, police reported exchanging gunfire with alleged carjackers in Watertown, a city near Cambridge. According to reports, one suspect has been killed during a car chase and the police are seeking another - believed to be the same person (known as Suspect Two) wanted in connection with the deadly bombing at the Boston Marathon earlier this week. (Photo by Mario Tama/Getty Images)
WATERTOWN, MA - APRIL 19: A woman asks a police officer when she will be allowed back to her home in a cordoned off area on April 19, 2013 in Watertown, Massachusetts. Earlier, a Massachusetts Institute of Technology campus police officer was shot and killed late Thursday night at the school's campus in Cambridge. A short time later, police reported exchanging gunfire with alleged carjackers in Watertown, a city near Cambridge. According to reports, one suspect has been killed during a car chase and the police are seeking another - believed to be the same person wanted in connection with the deadly bombing at the Boston Marathon earlier this week. (Photo by Mario Tama/Getty Images)
Shootings In Cambridge, Watertown Draw Massive Police Response
WATERTOWN, MA - APRIL 19: A woman asks a police officer when she will be allowed back to her home in a cordoned off area on April 19, 2013 in Watertown, Massachusetts. Earlier, a Massachusetts Institute of Technology campus police officer was shot and killed late Thursday night at the school's campus in Cambridge. A short time later, police reported exchanging gunfire with alleged carjackers in Watertown, a city near Cambridge. According to reports, one suspect has been killed during a car chase and the police are seeking another - believed to be the same person wanted in connection with the deadly bombing at the Boston Marathon earlier this week. (Photo by Mario Tama/Getty Images)
This frame grab from a video released by the FBI on Thursday, April 18, 2013, shows what the FBI are calling suspect number 1, front, in black cap, and suspect number 2, in white cap, back right, walking near each other through the crowd in Boston on Monday, April 15, 2013, before the explosions at the Boston Marathon. (AP Photo/FBI)
This frame grab from a video released by the FBI on Thursday, April 18, 2013, shows what the FBI are calling suspect number 1, front, in black cap, and suspect number 2, in white cap, back right, walking near each other through the crowd in Boston on Monday, April 15, 2013, before the explosions at the Boston Marathon. (AP Photo/FBI)
This frame grab from a video released by the FBI on Thursday, April 18, 2013, shows what the FBI are calling suspect number 1, front, in black cap, and suspect number 2, in white cap, back right, walking near each other through the crowd in Boston on Monday, April 15, 2013, before the explosions at the Boston Marathon. (AP Photo/FBI)
WATERTOWN, MA - APRIL 19: Police with guns drawn search for a suspect on April 19, 2013 in Watertown, Massachusetts. Earlier, a Massachusetts Institute of Technology campus police officer was shot and killed late Thursday night at the school's campus in Cambridge. A short time later, police reported exchanging gunfire with alleged carjackers in Watertown, a city near Cambridge. It's not clear whether the shootings are related or whether either are related to the Boston Marathon bombing. (Photo by Mario Tama/Getty Images)
Shootings In Cambridge, Watertown Draw Massive Police Response
WATERTOWN, MA - APRIL 19: Police with guns drawn search for a suspect on April 19, 2013 in Watertown, Massachusetts. Earlier, a Massachusetts Institute of Technology campus police officer was shot and killed late Thursday night at the school's campus in Cambridge. A short time later, police reported exchanging gunfire with alleged carjackers in Watertown, a city near Cambridge. It's not clear whether the shootings are related or whether either are related to the Boston Marathon bombing. (Photo by Mario Tama/Getty Images)
Police officers aim their weapons Friday, April 19, 2013, in Watertown, Mass. A tense night of police activity that left a university officer dead on campus just days after the Boston Marathon bombings and amid a hunt for two suspects caused officers to converge on a neighborhood outside Boston, where residents heard gunfire and explosions.(AP Photo/Matt Rourke)
Police officers aim their weapons Friday, April 19, 2013, in Watertown, Mass. A tense night of police activity that left a university officer dead on campus just days after the Boston Marathon bombings and amid a hunt for two suspects caused officers to converge on a neighborhood outside Boston, where residents heard gunfire and explosions.(AP Photo/Matt Rourke)
Police officers aim their weapons Friday, April 19, 2013, in Watertown, Mass. A tense night of police activity that left a university officer dead on campus just days after the Boston Marathon bombings and amid a hunt for two suspects caused officers to converge on a neighborhood outside Boston, where residents heard gunfire and explosions.(AP Photo/Matt Rourke)
A vehicle carrying officers in tactical gear arrives at the Watertown neighborhood of Boston, Friday, April 19, 2013. Reports of explosives being detonated and police are telling reporters to turn off their cell phones. Dozens of officers and National Guard members are in Watertown, where television outlets report that gunfire and explosions have been heard. (AP Photo/Julio Cortez)
A vehicle carrying officers in tactical gear arrives at the Watertown neighborhood of Boston, Friday, April 19, 2013. Reports of explosives being detonated and police are telling reporters to turn off their cell phones. Dozens of officers and National Guard members are in Watertown, where television outlets report that gunfire and explosions have been heard. (AP Photo/Julio Cortez)
A vehicle carrying officers in tactical gear arrives at the Watertown neighborhood of Boston, Friday, April 19, 2013. Reports of explosives being detonated and police are telling reporters to turn off their cell phones. Dozens of officers and National Guard members are in Watertown, where television outlets report that gunfire and explosions have been heard. (AP Photo/Julio Cortez)
WATERTOWN, MA - APRIL 19: A police officer lifts police tape for a police car to pass under on April 19, 2013 in Watertown, Massachusetts. Earlier, a Massachusetts Institute of Technology campus police officer was shot and killed late Thursday night at the school's campus in Cambridge. A short time later, police reported exchanging gunfire with alleged carjackers in Watertown, a city near Cambridge. According to reports, one suspect has been killed during a car chase and the police are seeking another - believed to be the same person (known as Suspect Two) wanted in connection with the deadly bombing at the Boston Marathon earlier this week. (Photo by Mario Tama/Getty Images)
Shootings In Cambridge, Watertown Draw Massive Police Response
WATERTOWN, MA - APRIL 19: A police officer lifts police tape for a police car to pass under on April 19, 2013 in Watertown, Massachusetts. Earlier, a Massachusetts Institute of Technology campus police officer was shot and killed late Thursday night at the school's campus in Cambridge. A short time later, police reported exchanging gunfire with alleged carjackers in Watertown, a city near Cambridge. According to reports, one suspect has been killed during a car chase and the police are seeking another - believed to be the same person (known as Suspect Two) wanted in connection with the deadly bombing at the Boston Marathon earlier this week. (Photo by Mario Tama/Getty Images)
WATERTOWN, MA - APRIL 19: A woman asks a police officer when she will be allowed back to her home in a cordoned off area on April 19, 2013 in Watertown, Massachusetts. Earlier, a Massachusetts Institute of Technology campus police officer was shot and killed late Thursday night at the school's campus in Cambridge. A short time later, police reported exchanging gunfire with alleged carjackers in Watertown, a city near Cambridge. According to reports, one suspect has been killed during a car chase and the police are seeking another - believed to be the same person wanted in connection with the deadly bombing at the Boston Marathon earlier this week. (Photo by Mario Tama/Getty Images)
Shootings In Cambridge, Watertown Draw Massive Police Response
WATERTOWN, MA - APRIL 19: A woman asks a police officer when she will be allowed back to her home in a cordoned off area on April 19, 2013 in Watertown, Massachusetts. Earlier, a Massachusetts Institute of Technology campus police officer was shot and killed late Thursday night at the school's campus in Cambridge. A short time later, police reported exchanging gunfire with alleged carjackers in Watertown, a city near Cambridge. According to reports, one suspect has been killed during a car chase and the police are seeking another - believed to be the same person wanted in connection with the deadly bombing at the Boston Marathon earlier this week. (Photo by Mario Tama/Getty Images)
This frame grab from a video released by the FBI on Thursday, April 18, 2013, shows what the FBI are calling suspect number 1, front, in black cap, and suspect number 2, in white cap, back right, walking near each other through the crowd in Boston on Monday, April 15, 2013, before the explosions at the Boston Marathon. (AP Photo/FBI)
This frame grab from a video released by the FBI on Thursday, April 18, 2013, shows what the FBI are calling suspect number 1, front, in black cap, and suspect number 2, in white cap, back right, walking near each other through the crowd in Boston on Monday, April 15, 2013, before the explosions at the Boston Marathon. (AP Photo/FBI)
This frame grab from a video released by the FBI on Thursday, April 18, 2013, shows what the FBI are calling suspect number 1, front, in black cap, and suspect number 2, in white cap, back right, walking near each other through the crowd in Boston on Monday, April 15, 2013, before the explosions at the Boston Marathon. (AP Photo/FBI)
This frame grab from a video released by the FBI on Thursday, April 18, 2013, shows what the FBI are calling suspect number 1, front barely visible at bottom left, and suspect number 2, in white cap, back right, walking near each other through the crowd in Boston on Monday, April 15, 2013, before the explosions at the Boston Marathon. (AP Photo/FBI)
This frame grab from a video released by the FBI on Thursday, April 18, 2013, shows what the FBI are calling suspect number 1, front barely visible at bottom left, and suspect number 2, in white cap, back right, walking near each other through the crowd in Boston on Monday, April 15, 2013, before the explosions at the Boston Marathon. (AP Photo/FBI)
This frame grab from a video released by the FBI on Thursday, April 18, 2013, shows what the FBI are calling suspect number 1, front barely visible at bottom left, and suspect number 2, in white cap, back right, walking near each other through the crowd in Boston on Monday, April 15, 2013, before the explosions at the Boston Marathon. (AP Photo/FBI)
This frame grab from a video released by the FBI on Thursday, April 18, 2013, shows what the FBI are calling suspect number 1, in black cap, left, walking ahead of suspect number 2, towards top right in white cap, through the crowd in Boston on Monday, April 15, 2013, before the explosions at the Boston Marathon. (AP Photo/FBI)
This frame grab from a video released by the FBI on Thursday, April 18, 2013, shows what the FBI are calling suspect number 1, in black cap, left, walking ahead of suspect number 2, towards top right in white cap, through the crowd in Boston on Monday, April 15, 2013, before the explosions at the Boston Marathon. (AP Photo/FBI)
This frame grab from a video released by the FBI on Thursday, April 18, 2013, shows what the FBI are calling suspect number 1, in black cap, left, walking ahead of suspect number 2, towards top right in white cap, through the crowd in Boston on Monday, April 15, 2013, before the explosions at the Boston Marathon. (AP Photo/FBI)
This image taken from video released by the FBI on Thursday, April 18, 2013 shows what the FBI are calling suspect number 1, front, in black cap, and suspect number 2, in white cap, back right, walking near each other through the crowd in Boston on Monday, April 15, 2013, before the explosions at the Boston Marathon. (AP Photo/FBI)
This image taken from video released by the FBI on Thursday, April 18, 2013 shows what the FBI are calling suspect number 1, front, in black cap, and suspect number 2, in white cap, back right, walking near each other through the crowd in Boston on Monday, April 15, 2013, before the explosions at the Boston Marathon. (AP Photo/FBI)
This image taken from video released by the FBI on Thursday, April 18, 2013 shows what the FBI are calling suspect number 1, front, in black cap, and suspect number 2, in white cap, back right, walking near each other through the crowd in Boston on Monday, April 15, 2013, before the explosions at the Boston Marathon. (AP Photo/FBI)

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