Here is a big problem. The is no GUN problem in America ( as a country, may be different for some areas ). I live in Arizona, where there is VERY little gun control. If you are over 18 you can go buy a semi-automatic rifle for 500 $ with 10 minutes of paperwork. Now , does this mean I am going to go kill people with it? No. If you make guns harder to get, it just makes the common man more frustrated. If these spree killers did not use guns, it would be poison, or a bomb , or hell , a homemade flamethrower ( 40$, two hours of work, and a can of butane ). If I am a criminal and I NEED a gun, I would just go visit shady joe over on 32nd street. There are bigger problems than the guns.'
1) Media, if every spree killer is going down in history, who's the next joe who is going to be ready to kill himself in his basement because he is mentally sick/afraid of the end/anti-social/ready to die, who sees these people going out with a bang, decides "Hey, I am already going to hell, might as well top off my drink before I go!"
2) Gunz ar bad! attitude, a lot of people have the attitude that guns are nasty evil things that kill people, no, guns are inanimate objects that spit lead. Where the lead goes is not up to the gun, but who is pulling the trigger. Imagine, what if ONE person in that school was carrying a gun.
"Self-Armament is the key to a peaceful society" - Fallout New Vegas
Now, this crazy psycho asshole wants to be famous, if he goes to the school and gets shot, game over. That would probably discourage any other fame getters now wouldn't it? Now I know what this looks like "Teachers should carry guns!" no, PEOPLE should carry guns. If that is a teacher, so be it. There are plenty of concealed holsters that would stop children from gazing at the gun and drooling because they want to be call of duty rockstars.
EDIT: Stop talking about banning guns in US. Its not going to happen. If it does, I will be hiding in my house, trying not to be shot by all the rioters.