Presumably the incident where the crazed lady stabbed the (unarmed) security guards could have been prevented by tazering her. Having practiced (simulated) knife combat, I'd certainly consider a long range weapon to be more effective than grappling.

If you are charged with protecting people from a crazy lady with a knife, would you turn down the tazer or gun? (If you believe it doesn't improve your odds of survival, you of course would.)

Given that many of these crazy people incidents happen away from security guards, it's hardly clear that "policing and security sets the tone". The US is just a highly violent place.

What sort of evidence are you looking for?