Shooting the leg of an approaching assailant is harder than it sounds, that's why every cop since forever is taught to go for center mass.

The father was at a range where if he tried some leg shooting trickery he risks being brained by the guy with he bat, the sons holding a shotgun so a leg shot would just lead to the man bleeding to death pretty fast since the femoral artery would probably be fucked.

I'm not weighing in on either side of this situation, too fresh for me to know what happened exactly, but the only time incapacitating someone with some fancy shot like that is possible is preemptively, in which case you just crippled a man who wasnt a serious threat to you (yet)