You just undermined thousand of years of military training and preparation. Yes you can be prepared and sure of your responses in actual combat before your first battle. It has been done since first militia was formed.I agree the cop should not face a civil suit, he should be facing capital punishment for failing his duties.
I'm talkng specifically about the civil suit, it's up to each service branch how they procecute deriliction of duty.
I disagree to a large extent with your assertion that you can predict accurately how anybody will react when face with a firearm assault situation, also the guy was a cop, not military, I doubt if the police have as rigorous a training regimen as the army, but military personnel are not exempt either from the fight or flight response inherent to being faced with a life or death situation. I know of military personnel who have committed suicide because they shirked their duty and some who have committed suicide because they followed orders and ignored their gut reaction to intervne.
Yes you can predict how a trained person will react and yes poluce force have extended training. He was no rookie also he had almost 10 years of sercice. Let's not pretend those basic facts you can google in 2.3 seconds are unknown to us.
Extended training doing what, though? Storming a building against an unknown number of shooters?
Capital punishment for that seems silly as well.