I don't think this is likely at all!
Firstly, I've read that Zimmerman has called 911 46 times since August 2011, and in every case reported young teens he considered suspicious. None of those calls reference an actual crime.
Secondly, I don't think the screams are Zimmerman at all. The narrative built up by the calls to me is quite clear.
- A neighbourhood watchman calls the police and says he sees a suspicious character in the neighbourhood.
- From 48 seconds into the call to around the 1m20 mark, he tries to play the South Park "he's coming straight for me" line... this is obviously Treyvon looking back at a guy who is staring at him on a phone. Bear in mind that at this point Zimmerman is stalking him from his SUV!
- When asked for a description - Zimmerman says "he looks black" (to be fair, the dispatcher asks for ethnicity and things like that)... but it is telling that Zimmerman feels like he "looks like he's up to no good, like he's on drugs or something". He wasn't.
- At 1:39 he expresses a frustration that "these assholes always get away"
- Only 2 minutes into the call, Treyvon starts running.
- At 2:08-2:20, you can hear Zimmerman's increasing anaerobic activity, and it has been suggested he says "Fucking Coons" under his breath at 2:22.... not an argument I'm interested in, frankly, it's irrelevant to me. The point is, Zimmerman is following him as he runs.
- The Dispatcher now asks "Are you following him?" -- "Yeah", responds Zimmerman -- "OK we don't need you to do that" -- "OK", responds Zimmerman... yet he continued to follow
In a subsequent call from a neighbour we hear the trail end of a pursuit and disturbance outside. We can hear screaming... not just a screaming, but a desperate shrieking - for help.
For Zimmerman to not be the aggressor - what would have had to have happened is for the chase to go, Scooby Doo style, from Zimmerman chasing Treyvon to Treyvon chasing Zimmerman. I just don't believe it. A man who patrols a neighbourhood like a wannabe cop and arms himself with a gun, chasing an unarmed man - knows how to handle himself, he doesn't have to run away or scream for help. And that voice sounds young. Treyvon's mother recognises it as her sons voice. While some might say she may just want to nail Zimmerman no matter what, I see no reason why I should trust the man who ignored officers, pursued someone and then shot them, over the mother of a murdered victim.
Right...i'm not trying to say he wasn't the aggressor, reread what I wrote. Have you ever been bullied? They are always the aggressor. And people are making to big of a deal on stuff that in the end is just going to distract from the main gist which is Zimmerman instigating all this. Theres nothing wrong at all with Trayvon standing up for himself and SOMETHING had to trigger a scuffle. Unless you truly believe Zimmerman just pulled out his gun and ran at Trayvon all Michael Mann style there was a confrontation. The prosecution is going to have establish the point where Zimmerman pulled his gun and shot him and the immediate events leading up to it.
A defense of a 17 year old half screaming for help puts him in a position of helplessness and THEN Zimmerman still shoots him in this weakened state? I don't find that credible or likely. A paper tiger bully who got stood up to, beat a little bit in a scuffle and then in panic pulls his gun and shoots, i find that much more likely in this case. Don't be emotional about it, think it through and keep in mind NONE OF THAT excuses Zimmerman and puts any blame on Trayvon.