I wonder what the advice from the police would be if a civilian found himself in a similar situation , shoot or back off. And if the civilian shot what would happen to them. Just a thought advice to civilians.
1.(The threat must be current, immediate, and unavoidable ).
I am not sure how that would happen as the lady was outside the house. Sometimes in similar situations they contain the threat , and try to negotiating. If he was contained he would not be roaming about killing anyone.should the cops wait until the lady caller doesn't show up for work the next day to see if she was stabbed to death, or maybe wait until the guy is roaming the neighborhood killing kids.....?