The OP's scenario was one of being out and about. What if it was back at the ol' homestead? We'll even make the following stipulations:
1) Broad daylight, clear weather, nothing obscurring the homeowner's visibility of the ne'er-do-well.
2) Therefore, the identity of the ne'er-do-well is easily discernable, and he's known to the homeowner. It should, therefore, be no real difficulty in simply phoning the cops and reporting it stolen by him.
3) He's stealing the grocery-getter truck out of the front yard, the homestead's only meaningful transportation into town to pick up supplies, the tools and material to maintain the homestead in a safe living condition, and food.
4) There are no firearms in the truck for the ne'er-do-well to be stealing, knowingly or not.
5) The ol' homestead is out in proverbial BFE, so there are no gas pumps or neighbor's houses which are liable to inadvertently stand in as a backstop.
Now, with all those stipulations, I'd still reach behind the front door, reach into the entryway closet, pull out the .308, step out onto the porch, level it, and aim CoM for the part of the ne'er-do-well I can see above the truck's waist line.
Who else would follow my example? Why or why not?