In any event, let's say the Rear Ends Sharpton and Jesse fantasy scenario have it right, poor little Trayvon was jumped by Z. Under Florida self defense law, even if you start a fight, once the other party starts using "deadly force" on you, you can respond in kind and self defense applies to his death at your hands. Blows to the head and smashing onto concrete aside, the second he reached for Z's gun he turned a fistfight into a deadly force encounter and justified his own homicide. End of story.
776.041 Use of force by aggressor.—
The justification described in the preceding sections of this chapter is not available to a person who:
(1) Is attempting to commit, committing, or escaping after the commission of, a forcible felony; or
(2) Initially provokes the use of force against himself or herself, unless:
(a) Such force is so great that the person reasonably believes that he or she is in imminent danger of death or great bodily harm and that he or she has exhausted every reasonable means to escape such danger other than the use of force which is likely to cause death or great bodily harm to the assailant; or
(b) In good faith, the person withdraws from physical contact with the assailant and indicates clearly to the assailant that he or she desires to withdraw and terminate the use of force, but the assailant continues or resumes the use of force.