Remember the Columbine shooters were building bombs at home, wearing trenchcoats, making threats, and doing stuff that back when I was that age would have set alarms off all over the place.
The 3 guns used by 25 year old Kimveer Gill - Montreal's Dawson College Shooter - were legally registered. What does this tell you about the effectiveness of the $1.5 billion gun registry?
"...doing stuff that back when I was that age would have set alarms off all over the place."
Doing stuff like that and I would be grounded until age 21 or so with no TV, no phone calls, extra chores...