Investigators inspect the roof of the Lord & Taylor store where a surveillance camera is placed, center, and an official said is crucial in the investigation of the explosions near the Boston Marathon finish line, Thursday, April 18, 2013, in Boston. Boston City Council President Stephen Murphy, who said Wednesday, April 17, 2013, he was briefed by Boston police, said investigators saw the image on surveillance footage they got from the department store near the finish line, and matched the findings with witness descriptions of someone leaving the scene. (AP Photo/Julio Cortez)