Boston Marathon Explosions

April 16, 2013 - 8:27 PM
Flowers are placed by a Boston police barricade 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 three people and wounding more than 170, were fashioned out of pressure cookers and packed with metal shards, nails and ball bearings to inflict maximum carnage, a person briefed on the investigation said Tuesday. (AP Photo/Winslow Townson)