It sounds like a Phantom.
http://www.funker530.com/quadcopter-sneaks-up-on-isis-tank-and-films-its-destruction/
http://www.funker530.com/quadcopter-sneaks-up-on-isis-tank-and-films-its-destruction/
You beat me to it. I was going to post.It sounds like a Phantom.
http://www.funker530.com/quadcopter-sneaks-up-on-isis-tank-and-films-its-destruction/