Hate to say it but he may very well have a good case against the establishment for negligence.
Yes, he’s going to win this case.
The seminal event was the gun being loaded in the first place. Handing the gun to the customer without clearing it compounded the error.
I’ve always received a weapon in the store after the employee has cleared it and locked the slide open.
After those two goofs, the store is liable, no matter how stupidly the customer behaves; because the inescapable truth is, nothing happens if the store does its job, no matter how stupidly the customer behaves. THAT is the reason these protocols exist, just in case the customer is stupid.
The guy is going to win his case.