|Winchester '73 (1950) [Joe Lamont]: Scalped (off-screen) by Rock Hudson; the scene ends as Rock attacks John. (Thanks to Gordon)
Westward the Women (1951) [Roy E. Whitman]: Fatally wounded in a battle with Native American warriors; he dies shortly afterwards while talking to Robert Taylor. (Thanks to Gordon)
A Lion Is in the Streets (1953) [Jeb Brown]: Shot by one of James Millican's thugs through the window of John's jail cell; he dies in the courtroom shortly afterwards while testifying despite his wound.
The Far Country (1954) [Sheriff Gannon]: Shot to death in a shoot-out with James Stewart.
Four Guns to the Border (1954) [Dutch]: Shot to death, along with George Nader and Jay Silverheels, during a battle with Apache warriors. (Thanks to Gordon)
The Kentuckian (1955) [Zack Wakefield]: Shot to death by Walter Matthau. (Thanks to Gordon)
Flaming Star (1960) [Sam 'Pa' Burton]: Shot in the back with arrows by a couple of Kiowa warriors while riding home; his body is shown again later on when his son (Steve Forrest) discovers him.
Seven Ways from Sundown (1960) [Texas Ranger Sergeant Henessey]: Shot by Barry Sullivan in an ambush; he dies shortly afterwards while talking to Audie Murphy. (Thanks to Gordon)
Dallas: Love and Marriage (1979) [Senator Sam Culver]: Dies (off-screen) of a heart attack. (John did not actually appear in this episode, but it's revealed in this one.) (Thanks to PortsGuy)
Cloak & Dagger (1984) [George MacReady]: Killed in an explosion by a hidden bomb on the plane he had hijacked. (Thanks to Robert)
Turner & Hooch (1989) [Amos Reed]: Stabbed to death by Scott Paulin and J.C. Quinn in John's waterfront shack.