If situation is as described, the use of the firearm was appropriate self-defense.
I’m 66, and in very good shape. I do not posses nearly the speed and strength I did half a lifetime ago.
If physically threatened I will always attempt to retreat to give myself all consideration in the eyes of the law.
However.......I cannot run away as, well, I cannot outrun most people & never could. I will not take a beating or heaven forbid, worse.
I can understand why this gentleman brandished his weapon as it stopped an assault dead in its track directed at him.
I would acquit if on a jury.
BTW - Here in Florida if you harm a senior (over 65) another 5 years is tacked on your sentence.