The eyewitness, John, who was closest to the attack, (it was right outside his window) said it was definitely Zimmerman calling for help. He saw and heard Zimmerman.
The loud bang was likely in the apartment of the caller, herself and the male in the apartment can be clearly heard moving around in the apartment making noise. I guess you are hinting at a second gun shot, that never happened.
I will rely on the eye AND ear witness, John, who was looking at what he was hearing, instead of an ear only witness, cowering in fear in her apartment, talking and making noise while ear witnessing.
No, not a second gunshot. I didn’t know if the bang was outside or in the apartment. If there are other 911 calls at the same time that will be clear.
Here is a list of transcripts, not sure it if it includes John’s.
http://news.blogs.cnn.com/2012/03/20/911-calls-paint-picture-of-chaos-after-florida-teen-is-shot/