I am a reserve police officer that was trained in knife fighting by a truly great instructor. The technique that he teaches can kill instantly from a few feet away. Once the attack begins you can't react quickly enough to defend against it even with a drawn gun. To defend against a knife attack that you know is coming the rule of thumb used to be 21 feet now it is 30 feet. Like the earlier leo poster I have seen very gruesome training videos about knife attacks.
It never ceases to amaze me how people on FR, that were not there and have no knowledge of how this incident went down, can armchair quarterback a tragic situation like this for both the girl and the officers.