My second thought followed on the heels of these three quotes:
Gill is believed to have been carrying at least three weapons: a handgun, a 12-gauge shotgun and a semi-automatic or automatic rifle.
He was armed with three weapons that media reports say were legally registered to him.
Neighbours told CBC Radio that Gill lived with his parents in the house.
His parents were "shocked", meaning they didn't know their son was amassing (and registering!) an arsenal of weapons to rival a Terminator. At least Harper isn't making any knee-jerk commitments; my initial thought is that this isn't a failing of legislation (at least not first): nobody needs that many guns.
Update: September 20: a related interview with the creator of the video game based on the Columbine shootings.
Update: October 2: Andrew Spicer suggested the idea of legislation that allows certain municipalities to ban certain firearms. I don't know whether that would work, but I do like the idea of formally recognizing that rural and urban municipalities have different concerns. I guess it could open us up to the confusion one can face crossing state borders down south, but, still, I feel the concept has merit.