He looks as he was attempting to throw, then changed his mind. Nevertheless, its the threat of throwing an deadly weapon. He has the capability to throw it, and was in a stance where he was able to do so. He has already used the weapon in a deadly manner in attempting to kill someone already. Seems appropriate to put him down if the officers felt there was a threat.
If the cops are coming at you with guns drawn, yeah drop the knife. I get it though. He was afraid of the cops because they took his legs.
He was mentally ill and disabled. He's not around anymore. The cops will have to find someone else to sate their bordem.
He already tried to kill one person and the police saw him as a threat. Sure, he needed help maybe he was a crackhead, who knows, but you can't help someone trying to kill you. I've been approached/accosted by random homeless/mentally ill people here in LA and they are pieces of shit and a waste of space. So I have no sympathy when violent psychos get what's coming to them.