Considering that a good chunk of police training is “Us VS Them” and “You gotta be quick on the draw if you want to see your wife and kids tonight” I can’t really blame the Acorn guy. He’s a product of the environment he was trained in. Any one of those windows could have a sniper in it. You don’t know who the detained person has backing him up. Kids with bikes can roll up on you and shoot you faster and easier than a squad of gangbangers can do a drive-by. Suspect could have smuggled a pistol with him and gotten loose.
The fact is, we train police to be afraid of everything, and then we give them a gun and send them out into society. This was a predictable result.