Rule 1: When survival is at stake do what you have to do and don't moralize it too much afterwards - Robert Heinlein, Tunnel in the Sky
Rule 2: "When it's time to shoot, shoot don't talk" - Tuco from "The Good, the Bad and the Ugly".
Rule 3: "You don't do anyone any favors by being soft", Starbuck BG
While I would not hesitate to pull the trigger to protect my family I would likely have an emotional reaction afterward. As it should be. Only the sociopathic criminals can take a life with out blinking decent God fearing people can recognize something is necessary but still feel sad that the deed had to be done
I would only regret and be sorry that someone placed my family in peril and me in the position of having to kill or maim the perps. I would be joyous if my family and my self were not harmed.