Hoolifer
Someone who is messed up in the head and thinks of multiple scenarios in their head, typically bad ones including murder or violence. They usually have a high anxiety level and/or depression with multiple mood swings a day. A Hoolifer can usually hide all these symptoms from someone, no matter how close they are to them. They also normally wear a hood or something to cover their face and prefer being alone and/or in the dark.
Hoolifer's are a very small group, but a very dangerous one because you don't know who could be one.