With flowers tied to a light pole next to them, Boston Police Superintendent William Evans, center, talks with an ATF agent at a barricade near the finish line of the Boston Marathon in Boston Tuesday, April 16, 2013. The bombs that ripped through the Boston Marathon crowd were fashioned out of ordinary kitchen pressure cookers, packed with nails and other fiendishly lethal shrapnel, and hidden in duffel bags left on the ground, people close to the investigation said Tuesday. (AP Photo/Winslow Townson)
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