What most excellent fortune to FIND a handgun on one's property the very same day that one is about to be robbed.
Sounds plausible though, and most fortunate that he was able to use it to good effect.
If that’s his story about the gun, so be it. What would you do in the same situation? Knowing that law-enforcement goes after law abiding citizens, instead of the scum criminals, I’d buy a throwaway gun too. Then deny it was mine if I had to shoot somebody robbing my business.