I was 7 when the Winnenden shooting happened (it's relatively close by). It doesn't come close to how bad some of the shootings in the US are but I still remember it as a core memory.
When your society isn't used to violence, a shooting sends an actual anti-violence message. In the states it seems to only instigate political drama and grifters and encourages more people to do the same.
I wanna say guns are the problem but that would be very naive. The easy access means the barrier of entry is SO much lower, allowing other problems to be magnified and lead to the actual shooting. It's such an insidiously deep rooted problem that I couldn't even begin to try to suggest how to fix it.