Sad to hear about his ending. Mr. Portis created one of my absolute favorite stories. The book is excellent, and the John Wayne version just about the most perfect movie adaptation that could be. I've watched that film over and over and over, never tiring of it, always finding something new in the characters, the story, even its philosophical depth.
[Little note to this obit: the author of it himself died in 2017. A reminder how the press has "death" at the ready to report.]
When I read the book, I was amazed to discover how faithful the John Wayne movie was. Scenes and dialog taken whole. It stops a little short of the actual end of the story, but that really doesn't do a lot of harm. The tone of the film really needed a more ebullient final scene than Portis' decidedly sad coda.
Charles Portis's work is definitely worth the time and trouble to track down. I read his short story for the Atlantic Monthly, "I Don't Talk Service No More" not long ago and found it moving. One of the greats.