The text of the Florida law says:
(3) A person who is not engaged in an unlawful activity and who is attacked in any other place where he or she has a right to be has no duty to retreat and has the right to stand his or her ground and meet force with force, including deadly force if he or she reasonably believes it is necessary to do so to prevent death or great bodily harm to himself or herself or another or to prevent the commission of a forcible felony.If you initiate an assault upon another, then you are engaged in an unlawful activity, and thus are NOT allowed to use deadly force.
The problem with this case, and with the law, is that there is considerable reason to believe each party believed he was being threatened and/or attacked and was acting in self-defense.