It is doubtful that the responding officers knew that the man was mentally ill but would that really change anything. Mentally ill people are just as, if not more, dangerous than sane people. You cannot judge unless you put yourself in any one of those officers’ shoes. They arrive on the scene of a person pointing an object that looks like a gun at people threateningly. You have to respond as if it is a gun. You show up and see the person with something that looks like a gun. You lawfully order him to drop the weapon and show hands or something similar. The man, who has been threatening people, ignores multiple lawful commands issued at gunpoint and turns and points what looks like a gun at you.
What the hell are you going to do? Are you going to hope it’s not a gun? What would your wife and kids prefer that you do?