Doesn't Canada have more guns per capita than the US? Don't know about the laws though.
Culture has a lot to do with it. A gun is a source of power, the ultimate comeback. If you have a gun, you have someone's life in your hand.
I think Columbine was the obvious tipping point and VT was just above and beyond that. The media attention and visible national outrage is all you need for motivation. If you feel so disenfranchised with society and life in general and you want to hurt as many as possible, this is what you do. You've seen on TV the pain and anguish it causes. To top it off, you die by suicide or in a shootout, you go out on your own terms. They never get their answers, they can only guess why you did what you did, and sure, they'll call you terrible things but they will obsess over you, want to find out any thing they can. Essentially you win.
Thats the train of thought thats scary as shit to me. Gun control can and will help curtail the ease of such actions, but its not going to stop people who feel like this. And if they can't do it with guns, they'll find another way to do it.