From a strictly legal perspective if the father had been armed and shot the guy in the head while he was committing the assault. The father would have been in good shape legaly even though he endangered his daughter from a passthrough, ect.
If the father kicked the guy in the ribs, knocking him free of the daughter before placing a round into his cranium, he has committed murder.
What's wrong with this picture?!?!?
Put me on the Grand Jury/Trial Jury and I can guarantee that the Dad walks in either scenario.
I would then be honored to take him to lunch after the verdict.