I'd be tempted to charge the 'victim' in this case. He was IN his house and went back outside off his property and confronted the alleged perps in their truck WITH his gun.
It may have printed or he may have said he had a gun, and that might have prompted the alleged perp to pull his pellet gun.
Not sure what the charge should be but he had no business going back outside and confronting them, IMO. At least improper discharge of a firearm near an occupied dwelling - a slap on the wrist and reminder not to do that kind of thing again.