My mate's mum used to work with a guy that ended up executing a taxi driver. He was a mentalist. When she heard he was a suspect, she was tempted to ring the police and be like 'yep that guy is fully mental'. But that's not really solid evidence for the police to go on. Apparently one of the things he said to her one time was, 'If I found out I had terminal cancer, one of the things I'd do before I died would be to put a gun to somebody's head just to see the look on their face'...