Federal agents released new evidence Tuesday on the Boston bombing saying it was done with kitchen pressure cookers packed with explosives,
nails and other lethal shrapnel.
Inside a pressure cooker bomb.
Boston bombs made with disturbing ease
Packed with shrapnel, pressure cooker bombs are crudely made but designed to cause maximum carnage.
Anatomy of a pressure cooker bomb
A look at the type of bomb that may have been used in the terror attacks at the Boston Marathon