After one blast went off at the finish line of the Boston Marathon this afternoon, people—reporters and spectators—grabbed their cameras only to witness a second blast in nearly the same location. One of the first videos from the finish line (above) shows many runners collapsing from the trauma of the blast. Below, victims are shown being wheeled away from the scene.

Panicked spectators heard the blast from a few blocks away:

A camera crew at the finish line was engulfed in smoke:

Boston police respond to the two explosions: