The bottom line is Australia's gun ban did not change their gun violence. They had one event before that was significant. They still have shootings. A person willing to kill everyone in their own family and turn the gun on themselves could very well walk into a mall and kill plenty. The ability is there.
In my travels around other countries, one think I noticed is the lack of general disgust with other people like here in the US. You see these people get into fights outside a nightclub in Sweden, one guy knocks the out of the other, dude falls, they roll him over and drag him off the sidewalk. Here in the US someone not even in the fray would run up and stomp his head, then someone else would steal his wallet. Hatred and lack of give-a- about people in general in this country makes mass killings just a step further than suicide. I don't get the thing with the kids, mental illness I suppose, but some others.. those people have lived lives of not really giving 2 s about anyone. Whatever causes that, I don't know. Maybe they weren't raised properly.