I had heard in a report [but cannot confirm the accuracy of it] that Martin basically cold-cocked Zimmerman and then jumped on him when he was on the ground.
During the scuffle, the gun on Zimmerman became visible. That is when the struggle for the gun took place, and during it, the gun was discharged ...
It will be interesting to learn how close the gun was to Martin when it was fired.
The description about the struggle for the gun is what I read too. If that’s what happened, we have a shooting to defend one’s life. Case closed.