I had a dream about killing my former roommate this morning. Is this a bad sign or what?

I haven't seen this guy in three years and I'm still holding a grudge. I must admit, forgiveness isn't one of my strongest points. I'd rather not go into what I would consider the hell that he put me through the entire year that I lived with him. In this dream, he was constantly haring me. It got to the point where I couldn't take it anymore and I just snapped. I picked up a knife and stabbed him repeatedly. I'm now wondering what caused me to have this dream. Is it because I hate this guy so much or is it because I watch too many horror movies? Or am I going psycho like Norman Bates? I've never killed anyone in a dream before. It felt good though.