What causes unwanted negative thoughts and how to stop them?

I’m just curious as to what causes it. Sometimes I have unwanted horrible thoughts that just pop up in my head. It’s nothing I desire but sometimes just pops up. It starts whenever I see horrible bad news or a show involving things such asmurder, rape, incest, betrayal, molesters, etc. and I think about myself in their shoes whether I’m the victim or the person.

Again, sounds crazy here. I have no desire to be in pain or cause pain. It’s not like I imagine, fantasize, or play out a scene but the thought after seeing that show or reading a news article of a story.

Example, recent story about a man I know killing his pregnant girlfriend. I was disgusted and mad…felt sad at the same time. But then the thought of what if it happened to me or whatever plays out and the thought is horrible but then pops up in my head and I suppress it. And this is absolutely nothing to do with my relationship though cuz my bf is not abusive at all lol.
Or it could be a scary movie I watch which I know I don’t believe in evil spirits or talking dolls but at night it’ll keep popping up in my head and scare the crap out of me even though I don’t want it to.