Martin “retreated”... while Zimmerman was paying attention to him. But, when Zim turned his back and walked away, Martin attacked from behind.
Poor little innocent skittle eatin’ honor student.
This all makes a lot of sense to even the most hardened person if you imagine Zimmerman having his pistol out.
Even by Zimmerman’s account, Martin did not attack from behind. He approached from behind, they had words, and he punched Zimmerman in the nose.