More photos: Boston Marathon Terror Attack
The scene at the finish line of the 117th Boston Marathon when one of the two bombs exploded.
A second explosion goes off (rear) as Bill Iffrig was blown to the ground by the first explosion near the finish line of the Boston Marathon
Victims of the explosion lay on the ground in shock at the scene of the explosion.
Police officers run with their guns drawn as they hear the second explosion down the street.
An injured person is wheeled across the finish line of the Boston Marathon.
Destruction and victims at the site of the explosion. Barricades hindered the help from getting to the injured.
Two officials run away from the first explosion.
People leave the bleachers at the finish line after the explosion.
An injured woman is tended to at the scene of the explosion on Boylston Street.
A woman looks on as runners pass near Kenmore Square after two bombs exploded during the 117th Boston Marathon.
Runners who had not finished the race were stopped before the Massachusetts Avenue overpass on Commonwealth Avenue.
A man comforts a victim on the sidewalk at the scene of the first explosion.
A victim is moved out of the scene in a wheelchair.
Boston Marathon runner, center, is reunited with loved ones near Copley Square following the explosion.
A child is comforted after explosions went off at the Boston Marathon.
A victim of the explosion is helped onto a stretcher.
A victim is helped on the sidewalk of Boylston Street.
Bomb victims are pushed to safety.
A man walks the scene of the explosions at the Boston Marathon.
A Boston Marathon runner is comforted in the aftermath of two blasts.
People tend to an injured woman.
A runner embraces another woman on the Boston Marathon route near Kenmore Square after two bombs exploded.
Katherine Swierk (left) is reunited with her aunt Terry Days (center) and friend Jocelyn Cacio outside Copley Square in Boston after explosions during the Boston Marathon.
Spectators were evacuated from the scene.
People on Boylston Street check their devices for news of the explosions at the Boston Marathon.
Justine Franco of Montpelier, Vt., holds up a sign near Copley Square in Boston looking for her missing friend, April, who was running in her first Boston Marathon.
Women desperate to hear from loved ones can't enter the scene at the marathon.
A couple run from the scene of the explosions with a stroller.
A frightened child is taken from the scene of the second explosion.
A man is helped with his bleeding leg at the scene of the first explosion.
President Barack Obama leaves the podium after speaking at the White House following the explosions at the Boston Marathon.
A woman prays at the scene of the explosion at the finish line of the Boston Marathon.