He's relentlessly coming at them and even if you shoot someone who could lunge at you with a knife, a bullet or two is not going to stop their forward motion. He's close enough to lunge at them. I've in fact, been trained that in my mixed martial arts training. If they lunge at you, even if you have a gun and shoot them, their blow could still deliver death. That is especially true with a longer weapon like a sword or bat. But a lunge with a knife can end you.

I don't see any malice here versus other vids we've seen. Others in authority may see it differently. But we're all amateurs unless someone was in law enforcement in this thread. I hate it happened but I don't think it was malicious from that video.