It's Zimmerman's voice. Zimmerman himself says it in the back of the police car that very night.
Zimmerman was placed in the rear of my police vehicle and was given first aid by the SFD. While the SFD was attending to Zimmerman, I over heard him state "I was yelling for someone to help me, but no one would help me."
I repeat again - unless you believe that Zimmerman knew that night that there was going to be a question about who was yelling for help, then you must agree that it WAS Zimmerman yelling for help.
That was a direct quote from the report of the SPD officer who cuffed Zimmerman that night.