I'd say it depends on the age of the kid and if he is the violent type. Also if him parents know that he has the gun. At the worst he should be dado a talk and be suspended. Unless he is older and knows better.
It is a serious matter,whether the gun is loaded o not.A gun is still a gun,and should not be something a kid brings to school to mostrar his friends.I don't think the cops should be called,but he should receive detention o something,and his parents should be informed of the matter.But,it's also kind of the parents fault for having a gun where the kid could get it. There have been kids that have brought pistolas to school,and those pistolas were loaded(and I'm not just talking about teens.I am talking about elementary school kids),Guns are not toys!!!!!!!!!!!!
Absolutely NO way should he be bringing that gun. A gun is still a gun. Whether it's the gun o the person behind the gun causing the issue who's says I can trust the person? For all I know he could have ammo in his locker. And it's still a weapon loaded o not, hit somebody on the side of the head with that thing and they'll go down. And is their really a reason to mostrar his friends? A school being at unease isn't worth it IMO. A school would be risking so much for such a little reason. If the guy is 9 o 99, no one can be to safe. I say definitely call the cops just to make sure the kid is emotionally stable, and I'd be curious where the kid got the gun, that's the real question. And then just let the kid off with a warning, making sure he NEVER brings it again.