That's a common training scenario, Jim. I've seen the citizen shoot the cop wrestling with the woman who ran into a bar. I've also seen the citizen shoot at the cop and hit me, the innocent patron! Will I be suing the Good Samaritan - what do you think?
I also once left a woman FOF participant to her fate while I vaulted over the fight and went to get help. Said victim later shot me in the back (she was the backup in a pawn store robbery) - she said I deserved for not helping her before -
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Such fun things and quick moral decision making doesn't occur in three gun matches.
Acting prosocially is very complicated as to the factors and motivations. Some in the gun world think it is dichotomous - you always act as the hero but that's BS. Dave Kenik (who I met at the NTI) had a good article on the superhero mentality and I've researched it. It's not simple as to an action - unless you proclaiming unconditional gun fight heroics on the Internet.