The Texas law that grants civil immunity in a justified self-defense situation applies whether it occurs in the home or in public. Here is the specific law (Texas Civil Practice and Remedies Code 83.001
CIVIL PRACTICE AND REMEDIES CODE
TITLE 4. LIABILITY IN TORT
CHAPTER 83. USE OF DEADLY FORCE IN DEFENSE OF PERSON
Sec. 83.001. CIVIL IMMUNITY. A defendant who uses force or deadly force that is justified under Chapter 9, Penal Code, is immune from civil liability for personal injury or death that results from the defendant's use of force or deadly force, as applicable.
Added by Acts 1995, 74th Leg., ch. 235, Sec. 2, eff. Sept. 1, 1995.
Acts 2007, 80th Leg., R.S., Ch. 1, Sec. 4, eff. September 1, 2007.
Of course, you are going to have to go to civil court anyway to determine whether the use of deadly force was justified under Chapter 9 of the Penal Code; but this would allow any suit to be dismissed at summary judgement, very early in the process. It also discourages "retribution" suits by making such cases even less attractive.