I don't think all drug dealers or generally criminals are mentally unstable people. I don't think 1 million people died because of mentally unstable people either, not so many would anyway. I agree that it's people who kill people, but they do it with guns. It's not that easy to kill somebody without a gun.
Did you hear about this thing with Yoko Ono, John Lennon's wife? She tweeted a picture of John's bloodied glasses and said something about 1 million people being killed in US by guns ever since his death.