He was running for the exit brathe. You cannot shoot and kill in such a situation and claim self-defense. Maybe if you shot him once or twice. But this guy continued to cap the guy even when he was on the ground. He wanted to kill him, not save himself. There is a channel called Active Self Protection (ASP) on YouTube. They review videos like these and explain what is acceptable for a selfdefender to do or not to. Shooting or chasing a fleeing suspect is highly discouraged.
His lawyer will argue that initially the accused intended to stop the thief from escaping the store, but upon wounding the defendant the guy still clutched at his weapon and tried to shoot back.
Provided the weapon was still in the assailants hands then it shows the man was a threat and having committed one crime at the scene, then the continuous volley of shots were meant to incapacitate him.
Take note that after disarming the thief no shot was fired at him.