Not sure special police training is required to decide if your life is in danger.
While I think his response was unwarranted at the point he shot, I could see escalation being his reasonable fear.
However, his training and experience as a cop should’ve made him more able to anticipate and defuse the situation. His retired cop status should’ve made the jury more doubtful of his actions. In many states, a retired cop still carries arrest powers etc. I think he had options.
In the end, his police elitism earned him an acquittal, in my opinion.