taking away guns doesn't make a psycho any less psychotic.
take away the guns, and then there will be bombs. Find a way to prevent the bombs, then they'll try poisoning the food in the cafeteria.
Those kids were out of their mind, but they weren't dumb. If they wanted to kill people, they were going to do it, and no one would have been able to stop them without some sort of Orwell-eque 1984, Big Brother, watching over them all day and all night.