If we ban guns then stories like the one I posted above would become more common. Instead of the relatively quick and painless shot to the head, people would be stabbed (We can't exactly ban knives), beaten to death, etc because unless we put every single person on Earth into a clear steel ball for all their lives, the murder rate will never be 0%.
I don't want to get too sidetracked on guns (as I said, it was a passing remark) - but you're completing misjudging why people murder. In cases like this, yes, these people probably had some sort of mental issue (and you have to ask whether we should be killing the mentally ill) or whatever. But a great plurality of murders aren't planned - if people have a moment of utter outrage, and there's a gun in the draw or handbag or whatever, it's just so easy - isn't it?
The US murder rate is three times that of the UK. It's fallen dramatically over here since handguns were banned. There's a distinct correlation (and almost certain causation).

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