I like to hurt people

I put notices on the notice board, and a girl turn up. Young girl. She was a second-year student. About nineteen. She said, "This is a personality test, isn't it?" I said, "Yes." She said, "I've got a bad personality. I like to hurt people." I thought she was winding me up. I said, "Okay, fine." So we went through the tests. When she was looking at the photographs of the mutilated bodies, the sensors showed that she was getting a kick off them. Her sexual reward center - it's a sexual thing - was fired up by blood and death. It's subconscious. It happens in milliseconds. She found those things pleasant.

...

"She told me she'd tried to join the RAF," he said, "because they're the only part of the Ministry of Defence that allow women to operate weapon systems, but they sussed her out and rejected her. So she ended up doing history. Hers wasn't psychopathy in terms of being a manipulative con man. She told me about her homicidal desire the minute she met me, which suggest she wouldn't score high on the trait of smooth deceptiveness. But at the core of psychopathy is a lack of moral restraint. If a person lacks moral restraint and also happens to get turned on by violence, then you end up with a very dangerous serial-killer type who lusts after killing and doesn't have any moral hang-ups about doing so. There must be people in the population who get turned on by killing but have moral restraints that prevent them from acting out their fantasies, unless they're drunk or tired or whatever. I guess she falls into this category, which is why she tried to join the RAF, so she could obtain a socially respectable opportunity to gratify her homicidal urges."

Jon Ronson: The Psychopath Test