Young Guns II (1990) on Netflix

The movie begins with the aging Brushy Bill Roberts narrating his story to a young historian. His claim? He claims that he is the famous outlaw William H. Bonney, alias Billy the Kid, who was supposedly shot and killed by Patrick Floyd Garrett in 1881. The old man gives a very convincing story on how he and Garrett, along with Arkansas Dave Rudabaugh, Chavez y Chavez, Doc Skurlock, and a few others led the outlaw life and avoided the law, as they were wanted men. Garrett, a friend of Billy's, was paid by John Chisum, a cattle king, to eliminate Billy the Kid. So, Garrett and Ashmun Upson set out on a journey to find Billy the Kid.