What I don't understand is why they didn't release the dog on him. They warn him about the dog, you can hear the dog barking, and he acknowledges the dog being used if he doesn't cooperate. At this point there is a immenat threat to self and others to the point that they can justify using the dog on him. They clearly had lethal force if the dog didn't work out.

I won't blame the cops for shooting him, I would too if a guy (who appears to be low IQ and likely unable to understand the results of his actions) with a knife came at me. I just don't understand why they didn't use a less lethal means that was not only available, but a command away from ending the situation.