There you go. Not in Texas (or Kentucky, or Florida, etc.). Without going into a Texas law research project - many states allow deadly force to prevent any felony involving the use of force - here, for example, you can kill a purse snatcher who is unarmed. Same goes for a person who punches a school volunteer or bus driver. All felonies involving the use of force. In addition, our courts say that "robbery" includes the escape with the goods, so that deadly force could still be used to stop the robbery even where the robber was fleeing. Next, the justification is usually decided at the point force is used. For example, in many places you can use non-deadly force to take back your property or someone else's (as here in KY). If you try to lawfully take back your property and the thief or robber then threatens you with deadly force ("exchanged gunfire") you can use deadly force in self-defense. Then, of course, texas is the one state that allows you to kill a thief, under some conditions, while he is fleeing. I think there is a pretty good chance these guys would be justified.