Flowers sit at a police barrier near the finish line of the Boston Marathon in Boston, Tuesday, April 16, 2013. The bombs that ripped through the crowd at the Boston Marathon, killing at least three people and wounding more than 170, were fashioned out of pressure cookers and packed with shards of metal, nails and ball bearings to inflict maximum carnage, a person briefed on the investigation said Tuesday. (AP Photo/Winslow Townson)
