Peter, an LTC holder carrying a handgun, decides to get some lunch, so he pulls into a local burger joint to eat. He parks and exits his vehicle whereupon he witnesses a man walking out of the restaurant and across the parking lot. Suddenly, another man comes running up and points a gun in the first man’s face. Peter, not wanting to be the victim of a robbery, drops to one knee while drawing his handgun. Still seeing the gun pointed at the first man, Peter decides to protect the would-be victim of robbery and fires his gun, striking the robber.
If there was in fact an armed robbery taking place, Peter’s use of deadly force is likely legally justified, because if we put Peter in the shoes of the third person (the first man in the example), Peter would be legally justified in using deadly force to stop the aggravated robbery. Thus, the law will deem Peter’s belief that the use of deadly force was immediately necessary as reasonable.
Source: Texas Gun Law: Armed and Educated published by Texas LawShield, LLP