Federal agents zeroed in Tuesday on how the Boston Marathon bombing was carried out -- with kitchen pressure cookers packed with explosives, nails and other lethal shrapnel. | More Info

Pressure cooker bombs suspected in Boston blast

AP

Federal agents zeroed in Tuesday on how the Boston Marathon bombing was carried out -- with kitchen pressure cookers packed with explosives, nails and other lethal shrapnel.

Pressure cooker bombs suspected in Boston blast

editor's picks