Perform what? The point I was bringing up was that if you keep guns in your house you are responsible for them. If your son takes a gun to school then you are held responsible. Keep them locked away from them, don't tell them the pin codes, don't give them keys to the locks unless you trust that they're a sane individual and you've raised them to use them.
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The mother knew her son had issues. Why she thought it was a good idea to provide him access to firearms is beyond my comprehension. If I had even the SLIGHTEST inkling that someone in my household was mentally unstable, I sure as shit would not let them anywhere NEAR a firearm.