Except Zimmerman did not know if Martin had a gun, or an accomplice. He would have had no assurance of the outcome, or even whether he (Zimmerman) would survive the confrontation.
On the other hand, we have the delicious irony that Martin thought he was pursuing a "queer-ass cracker" and was about to deliver a "thumping" to a white gay man on the encouragement of his girlfriend.
So the Feds are going to prosecute the victim of civil rights abuse using the same law that gay-bashing Martin violated prior to his death.
So typical of Bizarro World justice when the Left is in power.
There is not a valid case against Zimmerman, but that will not stop the Obama administration from trying to bring charges.