Sounds like Martin did not feel any pain from the bullet and therefore thought he was ok and likely was about to get off of Zimmerman since Zimmerman now had the edge. The bullet likely went right through his heart giving him a couple of seconds of conciousness and then death.
A fool kid in so many ways.
Whoever thinks a ‘double tap’ with a 9mm is necessary to kill a man.. Think again. DT is a good practice, however.