It wasn't very good police work. Cop should've been more aware of his surroundings, especially with no back up. If he hadn't backed himself into a dead end, he would've had more time to consider non lethal options. He put himself in danger and had to use lethal means to get himself out of it.
He damn near ended up like officer dinkheller
Murder of Kyle Dinkheller - Wikipedia
en.m.wikipedia.org
Yeahhhh this is not what you really need to do if you are in law enforcement .
As folks pointed out, dude was almost a goner and shooting a leg or blasting a taser wasn't going to stop a person driven off of insanity. Heads don't know that once a person is gone, its either life or death. The moment she grabbed the knife it was like the death angel granted the wish.
Suicide by cop.....