That's why I said that this is Texas and not Maryland.
Sec. 9.42. DEADLY FORCE TO PROTECT PROPERTY. A person is justified in using deadly force against another to protect land or tangible, movable property:
~ ~ (1) if he would be justified in using force against the other under Section 9.41; and
~ ~ (2) when and to the degree he reasonably believes the deadly force is immediately necessary:
~ ~ ~ (A) to prevent the other's imminent commission of arson, burglary, robbery, aggravated robbery, theft during the nighttime, or criminal mischief during the nighttime; or
~ ~ ~ (B) to prevent the other who is fleeing immediately after committing burglary, robbery, aggravated robbery, or theft during the nighttime from escaping with the property; and
~ ~ (3) he reasonably believes that:
~ ~ ~ (A) the land or property cannot be protected or recovered by any other means; or
~ ~ ~ (B) the use of force other than deadly force to protect or recover the land or property would expose the actor or another to a substantial risk of death or serious bodily injury.
http://www.bakers-legal-pages.com/pc/0942.htm
I don't see anything in there about having to run away from your attackers or not being able to shoot them in the back if they are leaving.
He had no other way to get his car back other than to nail them. The old boy needed to keep them from fleeing and he did so in a most reasonable manner.
Sissy run away from your attackers instead of nailing the suckers laws may be the norm in Maryland, but they are not the law in Texas.