what should I do?

I am afraid, this time. But more than that, angry. The person I wrote about, who lives in the room adjacent to mine, by the fire escape, in the apartment next door, just threatened my life basically. I never know if I go to feed the cats, in which I have to pass through the ....well I won't get into it, or coming home at night, or hell he could just crawl through the window. There is something dead in my room like a mouse or something....at least I think that's what it is....behind the walls or by the vent, somewhere, but not anywhere where I can find it and remove it. THe smell is horrible. I had to sleep in the abandoned room across the hall, where that girl was (she moved out). So congratulations, me, another shit living situation. According to ....well, the better time to move is October. This month.....I haven't been anyone's dream. I know that. God knows I fucking try. But I failed yet again. Anyhow, this guy....when I passed him in the hallway, said "Don't go putting any fucking notes under my door, you hear? You don't know who I am." It's true, I don't know who he is, although I am sure he really is violent, deranged and dangerous. The kind of person who would hurt someone innocent and enjoy it, be proud of it. Of course, he is popular, too. A classic sociopath. I have to try not to be hateful you know? Problem is, it just drags you down to the same level. Still, I may be forced to go to the cops, which is horribly stressful, and I've been forced to tell the landlord as well. I really am afraid I'll end up in the papers as another stalking or murder victim. If that happens, I want to make it clear who the perpetrator really is lest they get the wrong guy.