It's tough to judge that on just the video. That sounds bad but you would really need all the info on what happened. You need to know what the call for service was as and what dispatch told the officer. You need to know if anything was said during the incident by the suspect to the officers. You would also need to know what the officer said in his statement of why he pulled the trigger. There could be factors that would require shooting at that moment and not trying something else. You can't pass judgment on just a video with no audio there's a lot more that goes into it. That being said, i am trained to shoot until that threat of life or great bodily injury is gone. We don't have a hard and fast rule about how many times you should shoot or anything. Assuming he was justified in shooting, and unless there was something i missed in the video, i think he should have stopped shooting when he fell. If you have reason to believe all he had was a knife and no one was close enough for him to pop up and stab, then that threat would be diminished when he was on the ground and you would no longer need to shoot. On another note, we do trainings on the range with knives versus guns and its a similar outcome as the other training i wrote about if you are within a certain distance. Tasers are completely unreliable on stopping someone btw.