Members of the Houston Astros including Chris Carter, center, observe a moment of silence for the victims involved in an explosion at the Boston Marathon prior to the baseball game against the Oakland Athletics on Monday, April 15, 2013, in Oakland, Calif. (AP Photo/Ben Margot)
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.