What would your course of action be if you came across someone stealing something from your vehicle or house?

Consider full situation, including risk to others, and most likely most safe course of action for everyone.
Assess intruder.
Probably call police from a safe place.
Improve safety by movement.
When everyone is in safest position, assess whether it makes sense to confront or not. Probably not unless necessary.
Await police response.

However, in the past, the circumstances of discovery have dictated other immediate responses (and/or resulted in immediate reflexive reaction), such as immediately roaring like a lion and getting ready for action. Result: thief runs away immediately.

Comon wisdom says don’t confront. And generally I think I would be too cautious (= chicken) to do that. I think I’d just call 911 for the cops.

Historically, though, I’ve done the opposite. A couple of young muggers put a knife to to my throat and grabbed my purse in a subway station, and it made me so mad that I forgot all caution and grabbed it right back. Then I doled out the money to them and kept the purse with all the rest of the contents, including ID and credit cards.

I also hollered at an intruder in my yard and told a creepy guy to get away from me.

Who really knows what they would do until a situation arises? It can be hard to think clearly in a moment like that, so unless you’ve had good training and solid practice, I guess you’re likeliest to go with instinct.

As I said in another discussion, Your catching him stealing from you will make him flee or at least stammer a bit.

I accidentally caught two guys breaking into my parents house when I lived there. They had a really stupid excuse for being there—they said they were looking for Home Depot and wanted directions,

Anyhow, they were trying to get in a window because they didn’t think anyone was home.
I showed them some scrap metal in my backyard that might have been worth a few hundred bucks and offered it to them. They declined and went about their way.

A year ;later, I was shot in a robbery but not by those two,

Call the police, film the perpetrator from a safe distance.
Don’t interact.

If he’s in my house he gets shot, outside I the popo’s..Ditto with the car situation.

I’d say “Release the hounds!”, but I don’t have any.
I have a really big handgun, but I wouldn’t shoot them. I bought a big one just so when they see it, they will immediatly stop and run.

I’d get away and call 911. There’s nothing at my house worth risking injury over.

If some fool breaks in our house at night then I empty my tear gas ball launcher gun at him and quickly escape down our fire escape and call 911.

Observe and report from a safe distance – and call police asap.

BUT, besides carrying a pistol for my own protection there are other firearms inside my house. I might intervene to keep them from leaving with weapons that could make them more dangerous.