I agree, call the cops call the cops call the cops, then booby trap the entrance ways. Set up group strategy and exit plans in case he really does come knocking and it's not the typical pissed off guy spouting bs. Think about all the places he might be standing with his rifle if he does show up, where he might be able to aim it, and where the subsequent rounds might end up when he is firing(think what angle the bullets might come flying through the doors windows walls etc). Remember if he really does have an ak-47 the rounds have enough power behind them to penetrate walls, windows, doors etc, and keep moving a long ways after doing so. But to put your mind at ease it really doesn't sound like he is all that serious to me, if he really wanted to kill you he probably would have done it already and not said anything to anyone beforehand, just done it. Sounds to me like he is just trying to intimidate you. But irregardless good luck, be safe and aware of your surrounding, and start a personal relationship with Jesus Christ as soon as you can!!! Godspeed!!!