The attacker did not know how to use a gun, and allowed the gun to get within arm's reach of his intended victim.  I suppose he thought this was more threatening.  The "victim" appraised the situation, moved his neck and head just a bit out the field of fire, and in the blink of his eye used his right hand to disarm the guy.  I doubt this was staged.  This was just a guy who did not know how to use a gun against someone skilled in defending myself.  

I had a friend in high school who took some form of martial arts, and one of the drills was to disarm a guy with a gun with either a kick or by hand, and he got to where he could get the gun almost every time.  The thing is, in an attempted mugging, the gun is to defend the mugger, not to attack the victim.  So, when the victim decides to defend himself, he becomes the attacker and chooses the moment of the attack.  Not that I'd ever do it, but that's where the advantage lies, as it always does with the attacker: you get to choose the moment of the attack.

Max wrote:

http://news.yahoo.com/blogs/sideshow/man-turns-tables-shotgun-wielding-attacker-141851442.html

Note to self, if you get a hold of the gun, commit a mercy killing: put him out of our misery.

I find this implausible. The suspect turns over the gun without a struggle, and in fact it almost looks like he hands the gun to the victim. Although, I can't give a valid explanation why someone would stage something like this, or why the NOPD would post it on the interweb if it was staged. But if you've ever been to New Orleans, you know logic and reason don't often apply.