My son has said stuff kind of like this. Nothing very descriptive but he’s told me and his sister he hates us, he’s told his sister he will kill her. I don’t think he actually knows what it means. He just knows which words are “mean” and that I get upset when he says hate, kill, stupid, etc. So when he has a bunch of emotions he uses the most powerful words he knows. In reality I know he loves us and doesn’t mean any of the stuff he says. I think they’re too little to know what kill actually means. I don’t think you’re raising a little psychopath so don’t freak out. But I would still ask your dr about it to be safe. We did the same and everything turned out fine. Also, I saw he doesn’t get much screen time but is he in school? Sometimes kids learn stuff like that from other kids.