I Just Want Some Psychological Answer

Hey. My brother says that this happens to him quite often he's a year younger than me.Its been happening to me too for the past few years. For no reason at all ill just be day dreaming, or trying to go to sleep, & my mind just wonders into the wierdest scenarios. Imagining someone's head just being chopped off. Peoples faces in absolute terror. Violence. Last night I had the worst nightmare that was so disturbing. I wasn't even in it.just watching. A woman being abbused so bad by her husband. Then the husband torturing the mother by, I cringe just to say it, but by raping and murdering there own daughter. I woke up feeling terrorized and sick. I couldn't stop praying. Honestly that's whats been helping me. Praying to god. My brother on the other hand I'm more worried about. He's a year younger than me and tells me it happens way more vividly. When he's awake. Random thoughts of violence. It happens to me too, but with him it just seems more often, and more vivid. I was driving on the highway with him. I was driving. He was in the passenger seat. We were laughing and talking, it was at night. Then, suddenly he says. Hey wouldn't it be really ****** up if there was really a bother and sister, talking, like us, on the highway at night, and then SUDDENLY the brother just starts WAILING on his sister. Til she's dead. Brutally just starts wailing, , beating her up so violently til she's dead. After he told me this, he was almost crying about it. Saying "omg what's wrong with me, what's wrong with me?!"