So really the only question here is was the victim justified under 9.31? Based on the result I would have to follow the judgement of the officers on the scene and say his belief was reasonable.
Texas Statutes - Section 9.04: THREATS AS JUSTIFIABLE FORCE
The threat of force is justified when the use of force is justified by this chapter. For purposes of this section, a threat to cause death or serious bodily injury by the production of a weapon or otherwise, as long as the actor's purpose is limited to creating an apprehension that he will use deadly force if necessary, does not constitute the use of deadly force