Let me guess “excessive force”. (sarcasm)
All homicides in Texas are investigated by a Grand Jury.
From what I have seen, it is a pretty decent system with a significant number of “no bill” findings, which is to say the Grand Jury did not find sufficient evidence for charges to be brought against the individual.
Well, the shooter had already taken away two guns, so he might have reasonably assumed that the invader was unarmed and unlikely to use deadly force. He might have been better off if he had shot the other two since they hadn’t had any firearms removed from their persons yet.