This cop needed to be fired. Human action is faster than reaction. A person holding an un-holstered weapon down at their side can draw, fire, and get 2-3 accurate shots off, before someone who is aiming down the sights, ready to fire, can recognize the movement and fire his own weapon.
Use of force is judged by what the officer knew at the time, and what a reasonable officer would have done with that experience. Dude has a gun, is raising the gun at you. Yeah, its probably a suicide by cop. If its not, or if hes tired of you not killing him, he will kill you before you can do anything about it. Now you have a dead police officer, and the murderer has an extra gun, extra ammo, etc.
This guy needed to be fired. Some of the best cops I have seen have been military/combat vets. Some of the worst have been as well. It is my understanding he had other issues than just this situation, but I can't cite that at the moment