FILE - In this Monday, April 15, 2013 file photo, medical workers aid injured people at the finish line of the 2013 Boston Marathon following an explosion in Boston. Runner Lucas Carr can be seen in the upper center of the photo in the yellow Boston Bruins shirt. Carr, an Army Sergeant who served in the middle east, assisted several of the injured by applying tourniquets. (AP Photo/Charles Krupa, File)

Photo by: Charles Krupa

FILE - In this Monday, April 15, 2013 file photo, medical workers aid injured people at the finish line of the 2013 Boston Marathon following an explosion in Boston. Runner Lucas Carr can be seen in the upper center of the photo in the yellow Boston Bruins shirt. Carr, an Army Sergeant who served in the middle east, assisted several of the injured by applying tourniquets. (AP Photo/Charles Krupa, File)