Completely justified.

Cop yells "STOP, or I will shoot". Guy keeps moving in a quick manner like he's searching for something (like a firearm), so the cop shoots him.

There's this myth that seems to exist with the public that a cop has to wait for a guy to point and discharge a firearm at him before he can use force. No. A cop can use deadly force if he reasonably feels that he's in danger. And when you're telling a guy to freeze and he's frantically moving like he's going to grab something, that's enough of a reason to open fire.

I have no sympathy for people like this.

ALWAYS COOPERATE WITH THE COPS. There's absolutely nothing good that can come from resisting arrest, disobeying orders or acting a fool.