Stay hidden and get to a firing position that you should already have planned. At this point we all know giving them a target and somthing to film helps them more than you. Record what you can on your end. Let them chant at the wall. Wait for them to take it to the next level. If they take your sign, fuck it. it'll be worth more as video gold. Be the first to call police. Dont hang up and drop the phone. (Play up how scared you are if you can) You are the victim. There is no need to give them a warning. The first time they should know you are there is when one of their heads explodes. Say nothing. Lawyer. Make sure you have lawyer insurance now. US LawShield, its cheap and everyone should have it considering whats going on.