Nightmares--triggers?

I just had one of the two scariest dreams of my entire life (I am 19). I tend to be a very happy person and upbeat about life. I am non religious (so don't believe in demons, spirits, etc., so please don't mention it) and not a fan of the whole spooky/scary movie scene (haven't watched one in years). I am really interested in where this dream could have spurred from. I don't want to share exact details, because it is scary for me to even think about it. All I am willing to share is that it involved death. Not myself dying, but one I didn't know, and there was an extremely weird connection between me and that person's death. None of this is relevant to anything in my day to day life. I went to bed fairly stressed out, but not all that much more so than usual (typical college student), so I really don't see what this dream means or where it came from. I hardly ever remember dreams, usually because I am so exhausted when I sleep. The fact that one of my only dreams in a few months was a really demented dream scares me. Any ideas are much appreciated. Thanks!