Hospitals reported at least 144 people injured, at least 17 of them critically. At least eight children were being treated at hospitals.
The Boston Marathon is one of the world’s oldest and most prestigious races and about 23,000 runners participated. The race honored the victims of the Newtown, Connecticut, shooting with a special mile marker in Monday’s race.
A few kilometers away from the finish line and around the same time, a fire broke out at the John F. Kennedy Library. The police commissioner said that it might have been caused by an incendiary device, but that it was not clear whether it was related to the bombings.
The first explosion occurred on the north side of Boylston Street, just before the finish line, and some people initially thought it was a celebratory cannon blast.
When the second bomb went off, spectators’ cheers turned to screams. As sirens blared, emergency workers and National Guardsmen who had been assigned to the race for crowd control began climbing over and tearing down temporary fences to get to the blast site.
The bombings occurred about four hours into the race and two hours after the men’s winner crossed the finish line. By that point, more than 17,000 of the athletes had finished the marathon, but thousands more were still running.
The attack may have been timed for maximum carnage: The four-hour mark is typically a crowded time near the finish line because of the slow-but-steady recreational runners completing the race and because of all the friends and relatives clustered around to cheer them on.