Even if you do spot the behavior it's hard to get anybody to do anything. Where I live we had a guy who said he wanted to kill Police. He'd been arrested a few times and had a few run-ins in the past but society just wouldn't deal with him even though society knew damn well that he was fucked up. Then he finally got his way and shot a police officer dead. We have another guy who is a repeat offender and steals everything that's not bolted down. One day he was robbing a car and didn't like that a small dog attacked him.....so he raped it to death(let that sink in)...he's since been out of jail and slashed a guy's face with a knife. Some things just cannot be dealt with properly because society isn't structured to help fucked up people let alone deal with them when they act out.