@TheDMLair Usually in my games the PC of the missing player just catches a mild case of Black-And-White syndrome, losing their color and fading into the background.
@awstar11 My guess is that they figure the cop could've arrested the white guy, or tried to stop the three blacks, and this was the choice least likely to get the cop hurt.
This is a terrible metric by which to rate whether a cop did the right thing or not, mind you.
@AlysssaHazel Depends a lot on the author and setting. In my own setting, they're precursor aliens that are friendly towards humanity, similar to the Asgard of Stargate.