Not the best source, but apparently two of the agents who were involved in the death of Tamerlan Tsarnev (Boston Marathon suspect #1) had a training accident and were killed in the incident.
I think I need more tinfoil for my hat.
Internet craziness? Perhaps.
The only other real link I could find was Prison Planet.
Make of it what you will.
Via an Email…Thanks, Bob
ETA: Apparently 90 miles beat me to the punch
Here is another source. Take it for what you will. This is the Virginian- Pilot.
http://hamptonroads.com/2013/05/medical-examiner-confirms-fall-killed-2-fbi-agents