Point of fact here: The truck owner did not "shoot the thief because the thief stole his truck." The truck owner presumably shot the thief in self-defense because the thief produced a firearm threatening and then using deadly force on the owner of the truck!
I'll not debate the mistakes the truck owner made in getting to that point, but a private citizen carrying a firearm for self-defense and being met with a deadly force threat, shoots TO STOP THE THREAT, just as an LEO is trained to shoot to stop the threat in the course of doing that increasingly difficult job. Unless there is evidence to the contrary, neither private citizen nor an LEO "shoots to kill." That distinction is important and that mindset should be part of any reputable training in self-defense, concealed carry courses, etc. OR if the private citizen is carrying where a license/permit is not required (such as we now have here in Florida and over half of these United States), then they need either seek out quality self-defense training that includes training on "use of force statutes." Alternatively they need study those statutes very thoroughly on their own, which can be daunting. Otherwise, the legal consequences can be dire!