American police are so badly trained, or badly equipped, or both. The problem is that they simply don't know how to subdue someone with a weapon short of shooting and killing the person. They do this all the time. It's like, well, the easiest thing to do is shoot, so let's shoot.
Why not taser the guy? I'm astounded that our police force doesn't use tasers more often. If an individual doesn't put down a weapon when asked, it is probably because he or she is mentally disturbed. You can be a person holding a small knife, and there can be multiple policeman around you, but if you don't cooperate, they'll just shoot you. I saw a video of a guy in some city who was walking around with knife--older black man, no doubt mentally disturbed. The police arrive, in numbers, and surround the guy, who ends up standing with his back against some wall or wooden fence, with about 8 police officers in a semi-circle around him. He's still got the knife, won't put it down--and then they shoot and kill him. There is something badly wrong with police departments that cannot subdue a man with a knife who, once confronted by police, is not a threat to the public. I think many police are absolutely terrified of their own safety, which shouldn't be the case, and this is one reason they are quick to shoot.
If somebody is an immediate threat to the public, then, yea, shoot the person if necessary. But a man with a knife or even a machete who is confronted by multiple police officers is not a threat to the public--only to the police, and even that is doubtful as worst case he can be shot.
What do animal researchers or animal control teams do when they want to subdue an animal that might be dangerous? They shoot it with a drug-carrying dart of some kind, and the animal passes out. The work is done, the animal awakens and is released--still alive! Or they throw a net over an animal, or they tie an animal up. Even big, dangerous animals are caught--they are not just shot and killed. Yet when it comes to humans, the police apparently have no alternative to shooting other than tasering, and they don't seem to like tasering. It's kind of primitive policing, when you think about it.