What could possibly have been going thru the cops mind to convince himself he could get away with this?
Steroids.
And probably anti-depressants.
Every case this cop was involved with is going to be scrutinized. No way was this a one time event, it was probably the culmination of a long series of incidents.
Answer: He did not know he was being recorded. Not only that, but had he not been recorded he would (100%) have gotten away with what he did. The only reason anyone is talking about this is because some passerby recorded the incident, otherwise without that video that cop would definitely have gotten away with the shooting. A bit chilling to think of it that way - that the only reason he is even standing trial is because of pure ‘bad luck’ for him in the form of a stranger with a cellphone camera, and that if that had not been the case, that the cop would be back on the beat.