The climate/geography pictured, especially the tree, is identical to my own west of Austin.
To set a rifle like that means you aren’t wandering far from it.. maybe to sip out of a stream or do private business before you set camp. The owner got snatched by something or someone who didn’t see him set the rifle.
Question is, why was the guy there in the first place? Quite remote as the rifle was never noticed by anyone thereafter.
It is a mystery.
One of these scraggly bushes is what the tree in question would have looked like 132 years ago. Pretty cool mystery.
The Great Basin is a lot dryer than around Austin. The gun is probably in shootable shape, after a good cleaning. I bought a .20 .25 Winchester trapper lever action for 100.00 one time. It had zero finish on the stock, zero finish on the metal, and even had a small wood screw holding the stock on the receiver. I took it to the Dallas gun show in 1999 or 2000 and got 2500 for it! I was shocked. I also sold anything else I had with Winchester or Colt on it or WWII 1911 .45’s for huge profit.