TexasCHLforum.com

This video does re-inforce the action vs. reaction that CHL/LEO stated. Also I noticed an interesting reaction/tactic of the officer... as soon as the man pointed the gun at him, the officer moved his head behind the tree trunk while leaving his shotgun aimed, then moved his head out from cover for long enough to make the shot, then moved his head behind cover again for a second after the shot. Very smart move, maybe training or just human reaction, but a smart move none-the-less.

JLaw

Edit to add: I can see where this could be a bad situation for the officer if the man was truely intent on killing the officer, but maybe the officer was reacting on instinct? But still, the officer handled the stressful situation well, unfortunately the gunman forced his hand.