Simon,
Unfortunately, you can have all the laws regarding guns you want, but as long as there are those who are either too stupid to adhere to the law or refuse to comply with the law, you will not prevent these senseless acts of violence, intentional or accidental, from occurring.
Not being familiar with Canadian law, I will assume from your post that the Canadian gun laws are much stricter than the U.S., yet Canada is no stranger to similar gun violence as seen in the U.S...again, I will assume at a lower rate, but there nonetheless.
Ultimately, it revolves around personal responsibility...until such time as people accept that responsibility, nothing will change.
TYA