There have been instances already, where the “good guy with a gun” (black, ‘coincidentally’), was gunned down by the cops when they showed up. Apart from the obvious fact that the arriving coppers will not know, which of the currently lead spewing people are “the good guys”, thus will assume that they are all the aggressors, the fact that the “good guys with guns” would be non-white, they would then prejudicially assume that the non-whites are ‘obviously’ the bad guys, and that it is the white guy who is the “good guy”. And then you can rest assured, that the right wing media and the right wing politicians, will immediately disseminate the narrative, that the non-whites were the mass shooters, using it to further their white supremacist agenda. And when it inevitably is revealed that they are, as usual, full of shit, the propaganda damage will have already been done.