I'm sorry but I have to disagree. Just because she isn't paying attention to him doesn't mean he has more time. She had her arm thrown back and in the process of going to stab the girl in pink. As for the three ways you mentioned, I have to disagree with those as well. When you pull a firearm you are trained to fire until the threat is neutralize. You cannot know how the person will react, you don't know if the attacker is on something. Maybe you missed, the adrenaline in their system may be blocking out the pain and they could just keep going, as for the taser, they are not always guaranteed to work. As someone said in this thread already, both prongs have to make contact which could be obstructed by clothing, miss, or could have hit the other girl and still not had a good effect. And on the subject of disarming her, that is extraordinary dangerous and could only make things worse. They might not have been able to get the knife away from her, causing a struggle and fighting over a knife never ends well, the officer could have slipped and injured the other girl, or any number of other horrible things. I agree it is very sad that that girl died and it would have been better if none of this happened in the first place, but at the same time, she was actively attempting to stab that girl in pink. As sad as it is, when you are in a situation where every moment counts and are given little other choice, you have to make a decision right then and there. There are bad cops, cops that screw up, cops that make a bad judgment call, but this just isn't one of those cases. Had the cop not acted at that very moment that other girl could have been horribly injured or worse.