The Texas law in question goes back to the days of horse thievery. Several years ago, a guy shot a tow truck driver who was repossessing his car in the middle of the night. He shot at the guy with a scoped rifle.
The keys to the shooting were that he was taking property and it was night time. Texas has a whole bunch of laws that are defined by night or day -- like burglary laws.
In Killing of Repo Man, Law Shields the Killer
In the stated case, here, the guy did not get anything other than the poo scared out of him.
Once a BG is no longer a threat and is retreating you are taking your life, liberty, and fortune in your hands if you shoot him.
The rule of thumb is "When in doubt, don't."