This scenario is an almost total "no-win" situation.
Consider:
1. It's an actor in a scene you're not aware of. Highly unlikely, but hey, it's RatWorld where anything can happen, right?
You plug him, thinking he's a nut. Guess what RatWorld PR will turn you into, a gun toting nut. Now you've given more fuel for the gun banning fire.
2. It's a nut, but you miss. Oopppsss! Incoming fire is a b****! Now you're either dead, wounded, or in the middle of a firefight in a panicked crowd of kids and tourists.
Again, RatWorld PR (and the networks they own) will turn it into "Shootout at the OK Amusement Park" with you as the only surviving (maybe) loon to prosecute.
3. You hit the nut. Good job. But now Ratworld PR....you get the point. Plus his family might sue you and you could go to prison where you'll have to deal with nuts like him on a daily basis.
4. You and your family do a quick 180 and slowly (so as not to draw attention) walk away. If nut opens fire you'll have a head start on the panicked sheeple, if he doesn't (it's been known to happen) and RatWorld PD takes him away or puts him down, you haven't escalated the situation or exposed yourself.
1,2, and 3 are losers for you, 4 is the only winner.
Now if you placed this scenario in israel, then within a second or so there'd be 50 guns pointed at nut job and that would be the end of that.
If sheeple choose to go unarmed and are faced with an armed loony, then they shouldn't expect an armed citizen to take the risk and responsibilty they weren't willing to assume themselves to try and save them.