There aren’t really any automatic weapons in the US, unless they were manufactured before a certain date and you have a particular hard to acquire license. You may mean semi-automatic. I assume you don’t know many gun owners. I grew on a farm in the south and Incan assure you that when people there say “come and take them,” they mean it. At this point you’re talking about a lot of very armed veterans and hunters, it just doesn’t seem practical. If you could wave a magic wand, who knows it may work but that isn’t really an option.

I think there have to be other approaches here that can actually happen. The element of cultural memesis and role of the media in making anti-heros of these deranged young men is worth examining. It’s also pretty clear that the current approach to bullying in schools isn’t working at all. It also seems like it’s just too easy for some young men in their late teens to just fall through society’s cracks, I don’t know what the answer is there.

I think you're thinking of Siberia, not Serbia (the country ravaged by the Kosovo War in the late 90's).

Serbia is dominated by Belgrade, a dense city with population 1.7 million.

I second the sibling commenter in thinking you got it confused with Siberia.

Likely some clues about guns in Serbia here: https://en.wikipedia.org/wiki/Serbia_in_the_Yugoslav_Wars