Not enough info in the story.
So, the homeowner let them leave AND he did not disarm them? And for his trouble he gets wounded in the shoulder. Hopefully he learned something.
I was thinking the same thing. Did he let him leave and give him the gun back? I suppose one way to handle it would have been to unload his gun, hand it back to him, then shoot him dead with your own gun. “He pointed his gun at me, and forced me to shoot him” Clear self defense.