Report: http://www.foxnews.com/us/2013/04/15/explosion-reported-near-finish-line-boston-marathon-spokesman-says/
Footage [NSFW]: http://deadspin.com/explosions-reported-at-the-boston-marathon-473008941
What (who?) do ya'll think is responsible? Speculation begins now.
My prayers go out to everyone impacted by this terrible event. :-(