It's very glitchy, but here's the moment the bombs exploded near the Boston Marathon finish line, from WBZ's camera mounted there.
While the quality leaves a lot to be desired, it's the best shot we've seen so far of how and where the explosions occurred and how quickly first responders reacted to the event. Here's what ran on WHDH:
(Video removed by request of CBS. View it here.)
Intense video of the first explosion, from Steve Silva, Boston.com producer:
More coverage of the marathon bombing here.