Take the race component out, and I think you’re on firmer ground. This was a cop with an unreasonable fear that a civilian would shoot him. His training was obviously geared towards lethal force as a first resort, not a last resort, and that is a big problem. It seemed like a reaction more appropriate to a war zone by military personnel, not by police ordered to serve and protect.
The path forward here is a review of training and use of force guidelines. You cannot eliminate fear, but you can train better responses to it, such as creating distance, moving to cover, and calling in back-up.