With both men equally matched, and no way to determine good from bad, I would be strongly inclined to create distance, seek cover, and observe for more contextual information.
in general, i don't disagree with that. but if the bullets are already flyin, you don't have time to figure out what's what. OP said shootout had already started.Some of us believe interceding to stop a murder is not "unnecessary", even if it does place us at great personal risk.
Bingo!Find suitable cover, observe what else I can and dial 911.
Not my place to intervene in an unknown dispute.
Too many are blinded by delusions of grandeur thinking rushing headlong into a problem they know nothing about is smart, hoping to gain some recognition as a hero. That often makes matters far worse than they already were.