An occasional madman misuses a tool - so that tool is taken away from MILLIONS of law abiding people.
Of course, criminals retain the tool and the willingness to use it.
What will happen?
We don't have to guess. We have Australia's example.
Law abiding citizens had their means of self defense taken away from them and the police were overwhelmed by an explosion in violent crime by criminals emboldened by the knowledge that Australians could no longer defend themselves.