The article also states it is undisputed Zimmerman left his truck to follow Martin. IIRC, he left the truck to get a precise address to give to the police.
Florida Statute: 776.013 Home protection; use of deadly force; presumption of fear of death or great bodily harm.—
776.013(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.