FBI zero in on how Boston bombing was carried out, but still don't know who did it
FBI agents zeroed in on how the Boston Marathon bombing was carried out – with kitchen pressure cookers packed with explosives, nails and other lethal shrapnel - but said they still did not know who did it and why.
An intelligence bulletin released late yesterday includes a picture of a mangled pressure cooker and a torn black bag the Federal Bureau of Investigation says were part of a bomb.
