You don't think 9 kids can pummel a man to death? You don't need a gun to kill, the Marines taught me how to take away a knife from someone, flip his ass onto his back while breaking the arm of the assailant and then a hard Marine combat heel to the skull easily crushes him to death. No shotgun needed.
Maybe the kids just said they were gonna kill him?
A terroristic threat is only terroristic when it is obviously not being enforced at the time. If you call me on the phone and say your gonna kill me with your bare hands, does that mean I am justified to drive over and shoot you? If you yell the same thing at me from across the street and then walk away its the same thing, I am not justified in shooting you at all. On the other hand if you say that to my face and then come at me with your fists I get to shoot your ass, even if you only intended to scare me.
The whole defense pivots on the mind of the DEFENDER, if he truly thought his life was in danger beyond any reasonable logic, then he goes free.