Right, now you're starting to get it. The problem, however, is that the quick and easy solution is rarely the best.

First of all, judging by the rates of violent crime in your own country, I think it's safe to assume that the 1996 gun buyback didn't actually do anything. I sincerely doubt that gun buybacks in general are actually effective, even if the violent crime rate decreased afterwards. Correlation does not equal cause.

Second, the problems usually start in the public school system, which is why I mentioned the "public school to prison pipeline," in reference to the fact that the Prussian model (which American schools are based on) is an absolute failure, and @jacobtothe could explain why if you don't already know, because I can't be arsed to explain at the moment. I was spared from that experience, fortunately, otherwise I may very well have turned into a murderous psychopath... okay slight exaggeration there, but maybe you see my point.

Third, consider what I told you about the average school shooter, and bear in mind that not only are these (usually) boys abused at school, they are also neglected at home. Parents who don't want to raise their children stick them in public school and don't help them with their problems. Some people shouldn't be parents, simple as, but I don't think the government should be making the determination of who can or cannot be a parent; as before, Russia has this problem too, as @taliakerch routinely mentions.