The question here is regarding "another" person, a clerk, being held at gun point and whether anyone would take any action to end the act.
Let's change the question. Suppose it's you held at gun point. Not happy with that? OK, it's your teenage part-time-employee kid held at gun point. Does that change anything for you? What would you like me to do?
You see, I don't want to get involved. It's not my job, I'm not a LEO. As a matter of fact, since the BG didn't see me; I'm just going to crawl out the side door. Sorry! Call 911, they can take care of it. It's nothing to do with me.
I think I justified a withdrawal pretty well. It's nothing do do with me!
Otherwise, Texas law says...............
PC §9.32. DEADLY FORCE IN DEFENSE OF PERSON. (a) A person
is justified in using deadly force against another:
(1) if he would be justified in using force against the other under
(2) if a reasonable person in the actor's situation would not have
(3) when and to the degree he reasonably believes the deadly
force is immediately necessary:
(A) to protect himself against the other's use or attempted use
of unlawful deadly force; or
(B) to prevent the other's imminent commission of aggravated
kidnapping, murder, sexual assault, aggravated sexual assault,
robbery, or aggravated robbery.\
Hey, pardner; I'm sorry he's holding a gun on you. I know he might force you into the backroom and kill you there but, hey, this is none of my business and I've got myself to think of. I know you'll understand.