I read the story of this guy who killed some other guy who parked his car on his sidewalk, and also the guy's entire family. Then, when the cops came to arrest him he resisted arrest and shot like 3 cops. Eventually, when he was arrested and sent to court, he managed to slit the judge's throat with a shard of glass he had managed to conceal somehow. Some guys are just super-violent psychos, and for as long as they breathe they will keep hurting and killing people. The fear of legal punishment that works to dissuade normal people don't work on these guys, because their brains function differently and they are almost completely fearless.

