I think that’s it - that tree doesn’t look 100 years old, and would have grown around the gun.
Trees can grow extremely slowly in the west. There's a guy who takes core samples of trees in the Sandias and dates them, then seals up the hole and places a medallion with an event that occured when the tree first germinated. This one (I've seen a number of them) is less than 2 feet in diameter. And it's a Ponderosa pine, which grows faster than many of the Junipers.
It looks like part of a horse bridle hanging right by the rifle......I think I see a snaffle bit ant part of a rein or halter lead. The bear got ol’ Harvey AND his ride!