Boston Marathon Blasts

An injured person is loaded into an ambulance in the aftermath of two blasts which exploded near the finish line of the Boston Marathon in Boston Monday, April 15, 2013. Two bombs exploded near the finish line of the Boston Marathon on Monday, killing two people, injuring 23 others and sending authorities rushing to aid wounded spectators. A senior U.S. intelligence official said two other explosive devices were found nearby.

Medical workers aid an injured man at the finish line of the 2013 Boston Marathon following an explosion in Boston, Monday, April 15, 2013. Two bombs exploded near the finish of the Boston Marathon on Monday, killing two people, injuring 22 others and sending authorities rushing to aid wounded spectators, race organizers and police said.

Medical workers aid injured people at the finish line of the 2013 Boston Marathon following an explosion Monday, April 15, 2013 in Boston. Two bombs exploded near the finish line of the marathon on Monday, killing at least two people, injuring at least 22 others and sending authorities rushing to aid wounded spectators.

Medical workers aid an injured woman at the finish line of the 2013 Boston Marathon following two explosions there, Monday, April 15, 2013 in Boston. Two bombs exploded near the finish of the Boston Marathon on Monday, killing at least two people, injuring at least 23 others and sending authorities rushing to aid wounded spectators.

Medical workers aid an injured man at the 2013 Boston Marathon following an explosion in Boston, Monday, April 15, 2013. Two bombs exploded near the finish of the Boston Marathon on Monday, killing at least two people, injuring at least 22 others and sending authorities rushing to aid wounded spectators.

Two Boston Marathon volunteers hug each other, at right, as an injured person is loaded into an ambulance in the aftermath of two blasts which exploded near the finish line of the Boston Marathon in Boston, Monday, April 15, 2013.

Two police officers have rifles and watch from the roof of the Lenox Hotel overlooking the finish area of the 2013 Boston Marathon in Boston Monday, April 15, 2013. Two bombs exploded earlier in the packed streets near the finish line of the Boston Marathon killing two people and injuring more than 80 others.

Emergency responders aid a woman on a stretcher who was injured in a bomb blast near the finish line of the Boston Marathon Monday, April 15, 2013 in Boston. Two bombs exploded in the packed streets near the finish line of the marathon on Monday, killing at least two people and injuring more than 80, authorities said.