Texas Man with AR Rifle Drives Off Thieves: Lawful?

Houston TX-area homeowner Terry Willis was alerted to a swarm of car thieves amongst his driveway vehicles by his home security cameras around o-dark-thirty. His response? He stepped out of his home pointing an AR rifle he'd built himself, and told them "I don't think you want to do that." The car thieves fled in comic-like desperation. No property was taken, no shots were fired, no person was injured. Happy ending all around--or is it? Is the use of an AR rifle in defense of p...