Guest, you're not allowed to attack them until you believe you are in actual danger. Shouting "I'm going to kill you" over their shoulders as they run away is in a _very_ different league to shouting "I'm going to kill you" whilst running towards you. No matter if they do mean it at the time, they aren't threatening you at the time, so you do not under any system of justice have the right to shoot them. If they try to act on the threat then you can do what you like, but until that time it's just an empty threat.

As a police officer, Maxine has undoubtedly had many threats and insults shouted at her by drunken yobs after closing time. But so long as those yobs show no signs of crossing the street to accost her and don't throw bottles at her, they are free to shout.

Graham.