When Thomas Baker was confronted by two youths while out on a late night run he decided to defend himself.
Having been punched in the face and fearing his attacker was armed he pulled out a handgun from his pocket and shot dead the teenager who had hit him.
As the gun debate rages afresh across America in the wake of the Tuscon massacre, prosecutors in Florida have ruled Baker should not face any charges, even though 18-year-old Carlos Musteller did not have a weapon.
Citing the state's 'stand your ground' law they ruled the 28-year-old was entitled to protect himself.
Under the 2005 law people have the right to use deadly force as long as they 'reasonably believe' their life is in danger.
The controversial ruling will fuel the raging nationwide debate over firearms in the wake of the Tucson shooting.
Baker was out jogging alone after midnight near his home in Tampa, Florida, when he was confronted by Mustelier and a 16-year-old youth.
The teen told told police Mustelier decided he wanted to rob Baker, telling him: 'I'm going to bam him.. I'm gonna knock him out.'
Baker told investigators he was suddenly confronted by Mustelier who punched him in the face.
With his lip cut and suffering blurred vision he said he pulled out a handgun that was fitted with a laser sight and fired eight times
Mustelier was hit four times with hollow pointed bullets fired from the .45calibre weapon.
The 16-year-old told police he fled but remembers seeing Mustelier standing in the road with a red laser dot sight on his chest.
Baker, who had a permit to carry a concealed weapon, immediately called police after the shooting last November and stayed with the dying teen.
Later during a five-hour interview with police he said he feared Mustelier was armed.
He said he was carrying £500 in cash from fixing friends' cars and didn't want to lose the money.
Baker, who was out jogging to get fit before applying to join the military, said he always carried a handgun.