The various replies so far show that the situation can be complex.

I have actually run through the simulation many times personally ... knife against gun. The knife is a very effective weapon at short ranges (say less than 20 feet) and could be lethal against someone with a gun if they are not prepared. However, if the person holding the gun has their weapon already drawn and trained on the attacker with the knife- they should have very good confidence of subduing that attacker provided they keep a cool mind and can shoot accurately. The time factor is very small, so there's no room for error. But it could certainly be done if the gun owner is well prepared.

In the case of the original story - we just don't have enough info to evaluate exactly what happened. But the police officer has some good tactics that he could use. For example - take a position behind any parked vehicle, or behind a telephone pole, or even the seat at a bus stop. Any physical barrier. Then he could train his gun on the suspect and order him to drop the knife. The presence of a physical barrier would make it much, much harder for a suspect with a knife to do harm to the officer.

In reference to the comments about warning shots. I will speak my own mind - but it differs substantially from accepted procedures. I believe there is a definite place for "warning shots" or "warning blows" as a tactic, and that includes any lethal weapon (gun, knife, stick etc.). Anyone who is skilled with a weapon should be able to use it with sufficient accuracy that it can be used to deliver non-lethal force. That may seem like a high standard, but high standards are necessary if you want to save human life. Ask yourself a simple question ... suppose you are a criminal suspect standing 20 feet from a police officer. You have been ordered to comply with a police request. But you are hesitating. Now imagine that officer fires one bullet into the ground, just 12-24 inches from your left or right foot. Accurate shooting. Do you honestly think you are still going to ignore the commands that are given to you?? Not if you are even slightly sane. The warning shot gives the officer the opportunity to demonstrate his command over the situation. I think it's highly regrettable that this type of policy has been dropped as an option in US law enforcement. We are rabidly killing each other for no reason. It's not always necessary.

Pete #2