In this Monday, April 15, 2013 photo, Boston Firefighter James Plourde carries an injured girl away from the scene after a bombing near the finish line of the Boston Marathon in Boston. The FBI's investigation into the bombings at the Boston Marathon was in full swing Tuesday, with authorities serving a warrant on a suburban Boston home and appealing for any private video, audio and still images of the blasts that killed at least three and wounded more than 170. (AP Photo/MetroWest Daily News, Ken McGagh) MANDATORY CREDIT
Gallery: More photos from Boston explosion
Apr. 16, 2013 @ 01:16 PM
Investigators believe the two bombs that ripped through the crowds at the Boston Marathon, killing three people and wounding more than 170, were fashioned out of pressure cookers and packed with shards of metal, nails and ball bearings.