I'm not a psychologist, but I was a phone sex operator at one time.
One day I got a call from a guy who wanted to have a real conversation. He tells me where he's from, a bit about his profession, his age, hobbies; then asks me about mine. I gave him the details of my partially made up life. We crack jokes.
Then he tells me he wants to be sure I'm okay with the fantasy he has. He says he understands if I can't do it, not to be upset or feel like he is mad or that I need to do it at all. I thought that was really kind of him. He went on to explain what exactly he liked... Which was snuff. He asked me to watch a few videos (fake snuff) so I would understand what he likes,, and how to act for this call, all while reminding me I was under no obligation to do it.

Well. I've grown up watching America's Most Wanted, Cold Case Files, law & order SVU. I'm a bit fascinated by serial killers. I was afraid but I wanted to know his thought process and what made him tick.

So here goes: he wanted to pick up a prostitute, take her into a hotel room, act completely nice, and while she was undressing he would strangle her. Then have sex with her, tie her up and pose her, further desecrate her body, and wait for the story to hit papers. He made sure I mentioned the news stories. I would pretend to be a news anchor and mention how panicked the country was becoming.

I interviewed him, basically. I asked him when he developed these urges, and if he would ever do them in real life. He said he had always been fascinated by death, and when he was about 11 he began having fantasies about choking women. He explained he was trying to be ethical. He never wanted to truly harm someone else, but he couldn't help his urges, so he diverted them to phone conversations with consenting/well informed parties. It made me a bit physically ill to speak to him. My stomach felt empty, and I knew if I was ever in a room with him it would be the end for me. It's a terrifying feeling and it's given me a new perspective on victims of serial killers.