Canada has the same "let loony people wander" policy as the U.S. And thinking of our recent Waffle House shooter, both countries suffer grievously for doing so.
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I would draw your attention to the Canadian killer's inability to access firearms. It was no particular hindrance to committing mass murder.
How often do we need to say it? The issue is allowing crazy people to run free, not one particular type of weapon.
Almost anything can be a weapon, and most things have been used at some point. Tim McVey used sacks of chemical fertilizer and diesel fuel. Killers in London are using battery acid or butcher knives.
I defy you to control access to all possible weapons. We can warehouse the mentally ill, it isn't even a new idea but is very expensive.
