Two people were killed and at least 100 injured after two explosions went off near the finish line of the Boston Marathon on Monday as runners completed the race and thousands of people cheered them on.



Video from the scene showed two blasts about 20 seconds apart just off the course at the finish. The explosions occurred in the area of Boylston Street, police confirmed, as thousands of runners finished the 117th running of the Boston Marathon, with crowds watching and cheering at the finish. A third undetonated device was found near the finish line, a House Homeland Security Committee official and three law-enforcement officials told NBC News.



"All the sudden there was a massive boom. There was a sort of concussive blow that pushed a lot of people back. I could see runners falling in front of me," said Dave Abel, a reporter for the Boston Globe who was 10 feet from one of the explosions.

"When the smoke started to clear, I could see lots of bodies," he said. "I could see one woman staring vacantly into the sky. I could see a lot of mangled limbs, a lot of blood and shattered glass. It was probably the most horrific thing I've ever seen."



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Larissa Brinkley, who came from Pennsylvania to run the race, said people dropped everything and ran the opposite way. Other witnesses described what at first sounded like a cannon blast or fireworks.

"Then it went off again. And then all of a sudden we heard people crying and running away," said Serghino Rene, who was a few blocks away. "It was a huge horde of people just running away."