Point is, why would you walk towards the police with a knife at all? Maybe he couldn't get to them before they shot if he started running, maybe he could. Personally, I'm glad that we never had to find out. You DON'T move towards police with a knife drawn. You don't even need to raise your arm up like that, you can stab someone by running into them. Even if you've already been shot, if the momentum carries you - and your knife - forwards into the officer, they could die. I just think it's risky to start playing a game of "how little damage can we do to this armed person and still disable them"
There are almost always better ways you can handle a situation, but if you say "oh well they should have used a taser" then okay, let's run with that. Best case, the taser works and the guy is stunned. Worst case it doesn't take and you now only have one officer pointing a weapon. Which reduces your chance to hit the guy by a half. And even if you hit him, reduces your chance to disable him by MORE than half (one bullet in a non vital area may not stop you, where two might). Why are we trying to see how far we can go to protect this guy when lives of police officers are at risk? Even WORST case is when the officer lowers his weapon to get out his taser the guy charges, now you only have one officer shooting, and you don't even get the chance to attempt the taser. I just don't think we should be rolling the dice with the lives of police officers in a situation where the guy could have stopped the entire situation by dropping the knife and laying on the ground. He made a choice not to, and put the police in a position where they had to make a judgement call. It's always going to be easier to hit the guy while he's walking rather than sprinting at you, so I don't fault them at all for fireing when they had no idea what he was going to do next. All they knew is 1) There is a guy with a knife 2) he isn't cooperating with the police 3) he is advancing on the police. They don't know if or when he's going to start running, if he intends to kill them, hell, if he changed his mind and ran towards the civilians, what would they do then. At that point the option of shooting him is gone because you can't risk hitting the other people. What do they do then?
He put them in a position where they had to very quickly assess the situation and act. They may not have acted in the absolute perfect way, but they don't have full information, and they are only human. You can't fault them for responding in the way they are trained to respond, and for placing the lives of themselves, and the other innocents in the area, higher than that of an uncooperative man with a knife advancing on them.