Scrap thieves. It's 11c a pound right now. I took ~800# of junk down to the yard a few weeks ago, just a loose pickup load of crap we had lying around, and got $90.
Ninety bucks is a lot of dough to a guy that scraps. Most of us don't think about it. You steal a full-size pickup or old Chrysler Newport out of a field, that's $400.
I'm an insomniac with a gun. This is the wrong house.
By the way, there are no rules of engagement for civilians. Three warning and shoot? That's bullshit.
Generally, you can shoot to protect yourself unless you live in one of those pathetic eastern states. You go out to confront thieves, don't point a gun at them. Tell them the haul ass. If they attack you, shoot them. If they haul ass, call the cops.
Your axles have gone through the chopper by now. Sorry.