Memorial honors Boston victims

Marathon runner Nathan Finney of Boston and his daughter Mckenna, 5, gather with others ahead of an interfaith service with President Barack Obama at Cathedral of the Holy Cross, held in the wake of Monday's Boston Marathon explosions, which killed at least three and injured more than 140, Thursday, April 18, 2013, in Boston. (AP Photo/Matt Rourke)

People gather ahead of an interfaith service with President Barack Obama at Cathedral of the Holy Cross, held in the wake of Monday's Boston Marathon explosions, which killed at least three and injured more than 140, Thursday, April 18, 2013, in Boston. (AP Photo/Matt Rourke)

A photograph of Boston University student Lingzi Lu, who was killed in the Boston Marathon explosions, sits on a table as a student writes a message on a board outside the school's Marsh Chapel before a vigil, Wednesday, April 17, 2013, in Boston. The city continues to cope following Monday's explosions near the finish line of the marathon, which claimed three lives. (AP Photo/Julio Cortez)

A mourner reacts during a candlelight vigil in the aftermath of Monday's Boston Marathon explosions, which killed at least three and injured more than 140, Wednesday, April 17, 2013, at City Hall in Cambridge, Mass. (AP Photo/Matt Rourke)

Two theology students embrace following a vigil for Boston University student Lingzi Lu, who was killed in the Boston Marathon explosions, outside the school's Marsh Chapel, Wednesday, April 17, 2013, in Boston. The city continues to cope following Monday's explosions near the finish line of the marathon, which claimed three lives. (AP Photo/Julio Cortez)

Ethel Rose Paris holds up some religious items she brought to leave at the house of Martin Richard beyond a police cordon in the Dorchester neighborhood of Boston, Wednesday, April 17, 2013. Richard, 8, was killed in Monday's bombings at the finish line of the Boston Marathon. (AP Photo/Michael Dwyer)

Ethel Rose Paris holds up some religious items she brought to leave at the house of Martin Richard beyond a police cordon in the Dorchester neighborhood of Boston, Wednesday, April 17, 2013. Richard, 8, was killed in Monday's bombings at the finish line of the Boston Marathon. (AP Photo/Michael Dwyer)

Mourners pray during a candlelight vigil in the aftermath of Monday's Boston Marathon explosions Wednesday, April 17, 2013, at City Hall in Cambridge, Mass. (AP Photo/Matt Rourke)

Decenas de personas asisten a una vigilia por Martin Richard, en Boston, el martes 16 de abril de 2013. Richard, de ocho años, fue una de las tres personas que murió por las detonaciones en el Maratón de Boston el lunes. (Foto AP/The New York Times, Josh Haner) MANDATORY CREDIT; NYC OUT; MAGS OUT; NO SALES; TV OUT, NO ARCHIVE

Decenas de personas asisten a una vigilia por Martin Richard, en Boston, el martes 16 de abril de 2013. Richard, de ocho años, fue una de las tres personas que murió por las detonaciones en el Maratón de Boston el lunes. (Foto AP/The New York Times, Josh Haner) MANDATORY CREDIT; NYC OUT; MAGS OUT; NO SALES; TV OUT, NO ARCHIVE