You should always do just what the police say, or they just might haul off and shoot you.
I have thought out this same scenario because I always carry a weapon, even though there is a federal badge right next to it. I would never, ever attempt to do what this guy did and touch the holster.
Don't get me wrong, the police screwed up by not deciding who would be the "contact" officer, issuing commands. Those conflicting and incorrect commands caused this incident.