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Posted on April 17, 2013 at 7:46 AM
Updated Thursday, Dec 5 at 10:34 AM
FBI agents zeroed in Wednesday 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 didn't know who did it and why.
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Credit: Mohave County Sheriff's Office / KTNV