It looks like a genuine old gun, but a modern hack job. There were some originals that were cut down that way, but the tack-work is overdone. It just doesn't look right.
As for the blade on the buttstock... maybe a PhotoShop joke, as suggested above, but some 21st century gun hacker may actually have been dumb enough to do this. If that is the case, they have utterly ruined what may have been an interesting antique.
I have never seen or heard of a genuine antique shoulder arm with native associations that had been modified with a permanently attached blade like that. There were gunstock-shaped war clubs with metal blades, but these were not guns. Samuel Pond, who was a missionary to the Dakotas in the 1830's through 1850's, said war clubs of this type were very common, but they were mostly used for show: "The war-club was a flat piece of wood, two and a half feet long and nearly or quite an inch thick. It was made of hard, heavy wood, often hickory. At one end it was small enough to make a convenient handle, and at the other end about four inches wide, the broad end bending back much like the breech end of a gun stock. On the outside of the bend, six or eight inches from the end, an iron like a spearhead was inserted. The broad, heavy end was designed to give force to the blow. These clubs were highly ornamented, and were carried a good deal about home, as canes are carried by gentlemen who do not need them, but the war-club was not depended on much in battle" (from The Dakotas or Sioux in Minnesota As They Were In 1834, p. 357).
Notchy Bob