I agree. But we just don't know. And why would you re-holster it? That's what doesn't make any sense. Either drop it or continue to hold it. When the first officer arrived - put your hands up showing the gun and then slowly lay it down on the ground.
The fact that GZ had the presence of mind to re-holster it is odd. Especially since we have witnesses saying he was pacing and didn't answer people's calls as to what had just happened. Then he finally looks up and tells them to call police.
I do think GZ really thought TM had a gun and that if he shot it - it would be self defense. Once he did - and this again is JMHO - GZ went through his pockets and found that TM did not have a gun - hence the pacing and not answering.
JMHO if that was the case and the gun forensics back this up - GZ's goose is cooked - and I also think he knew that right after he shot him.
JMHO