A fixed camera at IDG's Boston offices captured the moment two explosions rocked the finish line of today's Boston Marathon. The camera shakes slightly at about the 9-second mark, and then smoke billows up at about the 15-second mark of the video, which runs 1:48.
After the smoke clears at about the 34-second mark, people can be seen running down Boylston Street. The Boston Public Library is the large building on the right side of the screen.
According to law enforcement officials, two people were killed and more than 40 were injured by the blasts, which occurred about 2:50 p.m.