Johnston was last seen at his girlfriend's apartment in Brigham City, Utah on July 22, 1981. He was involved in a physical altercation with Rudy Matthew Rebeterano inside the residence during the day. Rebeterano was seen shortly afterwards carrying a bundle wrapped in bedsheets out of the apartment. He placed the bundle in of the trunk of his 1972 Ford Torino and drove down Main Street.

Later that same day, Rebeterano's vehicle was located. Some of Johnston's belongings were inside the trunk, along with a large amount of blood. Blood was also found in the apartment. Johnston has never been heard from again. Rebeterano was convicted of second-degree felony homicide in Johnston's case and sentenced to prison; he has since been released. Johnston's remains have never been found but authorities are continuing to search for them.