Yeah one for the good guys but I won't be surprised if he is charged with at least manslaughter if it turns out he did in fact shoot the perp.
? Even in Canada where you aren't allowed to carry a hand gun anywhere but on the way to a Certified Firing Range, and Never loaded, a man shot and subsequently killed a person who was beating on him, and was never charged for that shooting.
I could not see this person (I don't know the facts yet) being charged with anything after stopping the shooter. Even if he does, I doubt a jury would.