I have mixed feelings about this but am hesitant to comment since I don't know what happened prior to the video starting, don't know the facts known to the shooter at the time about the decedent's verbalizations, actions, history of violence or being armed, etc.
All I'll say is that just because you're legal to bring a gun into a situation and shoot someone doesn't necessarily make it moral, ethical, or responsible. I probably could have shot multiple people in my life if I lived in Texas and approached every situation with this judgement.