Unarmed means nothing in the case, because it's the person's intent in pursuit of, and his forward action's in which created the situation that caused a huge concern for the person that was FLEEING or who otherwise was in retreat. The man was fleeing because he was justified in thinking that he was fixing to receive bodily harm with very deadly results if the attacker was allowed to get his HANDS on him.
I say this, and you can struggle to reply, otherwise don't bring your deadly fist or hands to a possible gun fight, because people have the right to turn and use deadly force if they feel threatened that they could be killed by those fist if the attacker catches up with them. This stuff is so simple.