Boston Marathon Explosions: Live Report
9:12 PM: The pair of explosions hit around 1900 GMT, a little more than four hours after the start of the race, as dozens of runners were crossing the finish line.
A video clip on Twitter shows an explosion going off -- just as the official race clock hit 4:09:44 -- apparently several feet back from the barricades and the line of national flags separating the sidewalk spectators and the street. One runner is seen staggering then falling onto his or her knees and back, while other runners kept going for a few more steps. Volunteers in yellow jackets covered their ears at the sound of the blast....
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