In their rush to release video of potential suspects, the FBI may have tripped up in their editing.
The first camera angle shows a man on the right fiddling with his ear (possibly adjusting or inserting an earpiece?), however, in the following camera angle the man is blurred out.
Was the FBI too lazy or too sloppy to blur the first angle featuring one of their agents?
An agent on site would definitely lend credence to the notion that there was a drill taking place before the race began, or that there was some form of prior knowledge of the bombings, which Boston Police Commissioner Edward Davis denied to intrepid Infowars reporter Dan Bidondi.