I did hear an interesting argument from an academic who was interviewed on our local news networks today - he suggested that these violent crimes are a symptom; that the perpetrators are being weaned on hatred from a young age, and are carrying out these violent crimes as a kind of catharsis. It's consistent with the testimony from survivors, who claimed that the suspect accused the victims of taking over "our" country and stealing "our" women and was trying to incite a race war. That's a pretty extreme point of view - it verges on Manson's "Helter Skelter" scenario - and it's not the kind of thing that you just pick up.
I don't think that you can tackle gun control head on. But if you treat these violent crimes as symptomatic of some kind of deeply-embedded cultural disease, then it will probably be easier to get meaningful change through, and much harder to resist it.