Somebody confessed to me that when she/he fantasizes of having sex with someone, quite often it ends up with him/her killing their lover usually with a shotgun on the head or with other ways, like a knife. The person said that it's even more often to fantasize of hurting someone while having sex with them but not to the point of killing and even more, fantasizes of being the one being hurt but I just can't understand why she/he would fantasize of KILLING them and take SEXUAL pleasure from that...is there some kind of condition that explains it? And is this person dangerous? He/she said they'd never actually do that but still...