If the guy bolts as soon as the shooting starts you do not have to assume anything because he is no longer a theat.
If he is no longer a threat you cant shoot him.
I assumed he was unarmed because he ran away and was not shot. But it really makes no difference.
If you want to go to jail, shoot a man in the back while he is running away.
Hindsight has its benefits. You go ahead and milk them...