kudos to the assailant, we don't often see training that includes acting to increase the tension in the air. How you train is how you fight, and most people only get the basic premise of a maneuver, and totally blank out when confronted with an angry unhinged person. The adrenaline and cortisol from a confrontation is powerful, so practice helps a lot.
But usually those people are experiencing a temporary distress, so it's far more preferable to subdue the individual in a way that does the least harm. Strip them of their weapon and then subdue or give them a little space. One person can be easily taken by a coordinated group, just isolate the limbs and apply leverage to limit movement. Of course each situation is different so we must put some trust in those with boots on the ground over hard and fast rules when it comes to responding to and neutralizing an armed threat.