What would this dream mean? Alright, so last night I had a dream about someone being murdered in my apartment, basically the floor right above me, and there's this guy who always plays loud music and throws stuff out his window (I'm guessing he's distressed), what would this mean?
Dreams don't always make sense, nor do they always have to make sense, although founder of the psychoanalytic field Sigmund Freud believed in dream interpretation: that dreams have a manifest content (literally what goes on in the dream) and a latent content (symbolic, not-initially-apparent meaning of the dream). It's worth noting there's no scientific evidence to back this up, and it's just something Freud believed. 

In the case of your dream, it could simply be that your mind associated your neighbor's aggression/distress with a display of aggression (homicide) and somehow connected the two in one dream. Freud would probably argue something along the lines of "Your repressed anger or frustration towards this individual manifests itself in the form of a dream in which he is murdered". Don't overthink this, and don't think your dream means anything bad. Dreams can be pretty bizarre.