Was there a round in the chamber to begin with?
When the cop racked the slide, it would/should have ejected, no? - (and one would have hoped someone noticed). So, it seems to me (and I do not consider myself an expert) that a magazine was in but the chamber was empty until the cop racked the slide.
Please do not read any of the above as excusing or minimizing the negligence/stupidity on both sides there. Just wondering about the actual sequence of actual events.
sounds like there was ammo in the clip if he racked it first