It is true that some individuals equate gun with danger no matter what. I have a few officers here that get itchy when they see open carry, not as I can blame them with the things they have to deal with. But honestly its an instinctual response for everyone. Past cases where uniformed officers have come upon a scene where off duty or private citizens had guns drawn, the officers in all cases I could remember always followed their force matrix. Physical presence, warning, ect. Many states teach this to their ccw citizens too. However, I've heard many fellow ex-friends and others utter sentences that they would shoot anything with a gun during a panic. GRRR. Honestly I think the chances of running into another ccw person in the area during such a situation is probably pretty rare. Or at least it seems to be. Those cases when it has happened, people were able to recognize and coordinate easy enough. I would have to imagine that the whole mannerism, stance, and feel of someone with a weapon drawn for defense is going to stand out in contrast to a looney toon massacre nut. The police should follow procedure, assuming the commands given are followed.
They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety.
---Benjamin Franklin, Historical Review of Pennsylvania, 1759.