Medical workers aid an injured woman at the finish line of the 2013 Boston Marathon following two explosions in Boston, Monday, April 15, 2013. Two bombs exploded near the finish of the Boston Marathon on Monday, killing at least three people, more than 140 maimed and wounded, and sending authorities rushing to aid wounded spectators, race organizers and police said. (AP Photo/Charles Krupa)
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.