My observation about the cops that did not shoot is because I do not know what the ROE was in the situation. (And it feels strange to be wondering about ROE in a civilian police setting.)
I would suppose that the standard “fear of bodily injury or death” is default, regardless of which agency is operating.
So, if four felt that standard had been met, what about the other eight? Or was in eighteen? I have seen different numbers as to total of LE present that day.
Maybe ten were recording?
I suspect that the shooters were snipers who were already alerted by tactical radio that an officer was in peril inside the restaurant. As this U/C cop was ejected for wearing false colors, the snipers were watching with extreme stress. If they saw a Cossack with a blade out, near the U/C cop being thrown out, BANG! Head shot. First Cossack killed.
Then it’s “sympathetic firing” by the other snipers with views of the scuffle turning into a police massacre.
Cops not behind a scope would not fire, they didn’t have the view or the awareness of the unfolding situation in front of Twin Peaks. You won’t just fire into a crowd because some others are firing.
But the snipers with the clear views from above sure would.