Those people required help long before they began shooting up people.

When trained personnel who's primary mission has always been to protect go on shootings like that. I'm sorry but the here the state has let them down. Their service is probably what has left them with those difficulties and the state discarded them. They should have had the proper care for the very real demons they were fighting long before they ever got to the point of shooting up schools.

For me that's not about gun control that's about the state you sacrificed for abandoning you and you deserved better from them. They let those people down and some of the blame falls at their feet. But sure you could also say less access less likely to occur. But let's use the UK as an example, guns (outside of sporting) are illegal to own to carry to whatever... And yet although very rare, shootings do happen, but are so rare because access to guns is difficult. And the shootings are done by sporting pistols/rifles/shotguns. So I'd argue that because those shooters didn't have access to military grade equipment the death toll was much much lower than it could have been.

Stabbings however, more or less the same as the US. People are going to break and do these things but the impact is lessened (from a quantity of lives lost perspective) when the access to higher capability weaponry isn't there.