I live in a country(Lebanon) that went through a 15-year civil war that ended in 1990. Guns are a fact of life here, they are very easy to get and lots of people have them. And yet nobody has ever gone into a school and shot children and parents that I know of.
We've had bombings, assassinations, terrorism, and even a war now and then. If it's violent, we've had it. But not this. Are Lebanese people better people? Hell no. But our societies tend to be more closely knit and more traditional. That has many many drawbacks but it also means that people very rarely get to such extremes in terms of mental well-being(to the point where they could do something like this) without being noticed.
I'm not saying traditional societies are the answer, don't get me wrong. I'm just saying, it's not just a choice between "bad people" or "too many guns". Reality is much more nuanced than that.