Let's extend that.
If Martin had been afraid, Zimmerman most likely would not have an apparently broken nose and multiple lacerations to the back of his head, because Martin would have fled rather than fight Zimmerman.
Remember, the scene of the death was not down some alley with no escape. It was on an open sidewalk with exits to both the north and south.
And if Martin had been afraid, and shot by GZ, he most likely would've been shot in the back, not the front.
It's the only thing that makes sense that would let Tray get away with killing GZ...and I do believe that's what he intended to do.