A SWAT team enters a hotel close to the finish line of the Boston Marathon in Boston, Monday, April 15, 2013. (AP Photo/Winslow Townson)
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.