The good news is that under critical incident stress, all the good guys should, in theory, be initially focused on the actual bad guy... afterwards, their will be an assessment phase OR you will be distracted by something else... if the "something else" is another good guy shooting, you need your Assessment mindset to be kicking in or bad things could happen. This is kinda related to realistic training for multiple threats, which we also covered recently on the show. If you still believe that defensive shooting against multiple threats is going to look like a Steel Challenge speed stage, it makes sense to expect the worst... luckily (in this case), that is not the way people actually behave in real fights when ambushed/surprised, so we can actually expect to have a "recognition" moment to assess whether or not we need to shoot the "other" guy(s) with guns. See the article in the newsletter I published today through the icetraining.us site for more on that. We also put out a DVD over a year ago ( I think) dealing with Multiple Persons in a critical incident, including people you want to protect who are unarmed, a friend that you might want to work with to solve the problem or just some other random CCW holder.
-RJP