BUT, what if one of the armed students has a perp on the floor and is standing over him with a gun? Then the police enter the scene and see this person with a gun aimed at somebody else on the floor.
Result...
The good armed student gets shot or, if they are lucky, is ordered to drop the gun -- into the perp's reach on the floor.
Really, folks, how are the police to be able to tell the difference between two armed students shooting at each other? Is the good student going to drop their weapon and let the perp shoot them or take them hostage? Tough scenarios!
I don’t think it’s realistic to expect that an armed student would ever “hold” a campus shooter at gunpoint. These shooters aren’t like bank robbers who have rational (yet criminal) goals and want to live; they’re coming in to kill as many students as possible and generally plan to off themselves anyway. The first warning of their presence will be when they start shooting and they won’t stop until they run out of ammo, choose to off themselves, or are physically stopped.
If there were some kind of hypothetical standoff or a student was holding a potential criminal at gunpoint, when the police got there they’d presumably demand that all parties drop their weapons to be taken into custody. The police would have no cause to shoot if no one was actively firing a weapon or pointing one at an officer. So in the scene you set up, well-trained police wouldn’t be shooting either person.
But as I said, I think the far more likely situation would be where the shooter comes in shooting and will not stop unless incapacitated. In that case, if there were an armed student who could return fire, the entire thing would be over in 10-15 seconds, and the student could holster his weapon long before police arrived.
I find it interesting that the worst case scenario the anti-gun nuts can come up with is that a carry permit holder who shoots an armed attacker may himself be shot by police. Even disregarding my above stated reasons why I think that’s unlikely, is it really the best they can come up with to say that no one should be able to defend himself from being shot because in a certain very specific scenario that person just might get shot by a different person? What nut is it who thinks it’s somehow better for the hypothetical student to be gunned down by an attacker than to be accidentally shot by police?
Yeah, tough scenarios, I don’t ever want to be in one. If I was, I would rather be the guy with the gun over the turd on the floor 10 times out of 10.