Violent nightmares as a kid

(TW: Ghore).

Hi everyone, I was recently talking about nightmares with my friends when I realized that nightmares aren't a problem for me now that I'm an adult. However, I used to have A LOT of nightmares as a kid, some of them were terribly violent and bloody. I'm gonna tell you one of them: When I was 11, I had this dream where I played with three other kids, one boy and two girls. However, they went missing and the investigation team needed me to help them find the kids. We ended up finding them in a forest. The boy had been dismembered, so was the first girl, and the other girl had been killed, her body left in a trashbag. Now, this dream is extremely violent for an 11 year old, especially when I never watched ghore content. Even today, this type of content terrifies me. Now, I'm wondering how is it possible to have such violent dreams, at such a young age with so many details