The more detailed that W6 can get, the better it is for the defense. Clearly he sees TM on top, the prosecution really doesn't attempt to counter it. He said he saw TM throwing down blows MMA style, prompted by the police interviewer or not, he agreed that it fit the description of what he saw. The prosecution attacked this because of the lighting and angles that W6 said he first noticed them. They questioned whether he could see anything specific or heard skin to skin contact. He conceded he didn't hear that and it seems to me thought about his choice of words and the conditions that given TM's back to him shielding what he was seeing, he could not say with certainty that TM was actually connecting with any blows or even that no blows were thrown and it was just forcible restraint. I think a demonstration by W6 is in order.
I have a difficult time buying that its TM calling to W6 for help for multiple reasons. As mentioned, he's clearly in the dominant position and if he is asking for help because he sees GZ's gun, you'd think he'd mention it or at least say to call 911. Also, W6 said his back was to him, so I'd at least look at the guy he's seeking help from. GZ wouldn't mention 911 because he had already called them and they were on the way and being in a defensive position would need immediate help. We can't say with absolute certainty who called out to W6 for help, but using reason and logic, we can make a pretty good guess. Austin also said initially the guy in red on the ground was screaming, though I'm not sure how much weight to give his statements (ie, he either didn't get that good of a look, or is leaving out some details since he doesn't mention seeing anyone else).