Tough to gauge. What did the officer see and react to? It had a look and feel to me of the officer perceived that the subject was accessing a gun and reacted to that. Any subsequent shots would have to be justified; if the person had and was still holding a gun and the officer believed there was still a threat, that may be articulable and lawful.
I no longer give ICE/CBP benefit of the doubt; I will not assume it was a good shoot til proven so. I want to know what the evidence shows.
Looked like an absolute shitshow of a ground fight. I want to know what kind of training those officers had. With that said, a subject proned on the ground who really wants to get their hands under them and access something is hard to stop from doing so.
EDIT TO ADD: Another quick rewatch on a small phone screen, even if he was armed those last 4-5 shots will be tough to justify.