Yeah, basically this. The whole 21 feet thing is based on something called the Tueller Drill. It doesn’t make sense in this context and shouldn’t be thought of as a rule.
There really should be some better way to handle these situations than what happened. This type of thing happens ALL THE TIME, where police get called to deal with a mental health crisis, the guy is armed with a knife, the guy isn’t actually going to stab anyone, but at the same time, the police aren’t going to let themselves find out if he is or isn’t, and so they end up shooting.
Seems like more aggressive use of bean bag rounds (which pack a serious punch) or pepper balls or maybe even a shield, a knife vest, and a baton, would work. Maybe a police dog could help in this situation. Must be other options. I do get it, once he has threatened someone with a knife, they’re going to need to disarm him and take him into custody. They can’t just leave after that. But they could handle it some other way.