I read your comment and largely agreed with you. Then I watched the video. It happened so fast, everyone was basically running during the attack (including the attacker and cops). It looks highly unlikely that the cop who shot could have grabbed the attacker before his partner got bludgeoned. And I don't know what prior information they had, but with a guy moving that quickly it'd be hard to distinguish a hammer from a knife.
My point is, this was a very fast-developing dangerous situation and I believe the cops responded well. Yes, cops are trained to handle dangerous situations but I don't think we can expect them to disregard other people's safety and lives to protect a very violent attacker.
"In real-world encounters, many variables affect time, which is the key component of the 21-Foot Rule. What is the training skill and stress level of the officer? How fast and agile is he? How alert is he to preliminary cues to aggressive movement? How agile and fast is the suspect? Is he drunk and stumbling, or a young guy in a ninja outfit ready to rock and roll? [...continues for a while...]"
I'm not sure what point you are trying to make. In our example, none of these questions about the suspect are known. So the officers have to assume that this attacker can (and in fact, he was in the process of).
My point is, this was a very fast-developing dangerous situation and I believe the cops responded well. Yes, cops are trained to handle dangerous situations but I don't think we can expect them to disregard other people's safety and lives to protect a very violent attacker.