Brent Mack, 50, was last seen alive on September 20, 2021, in Mulhall, Oklahoma. His daughter reported him missing on September 28 after she could not reach him for several days. The last known person to see him was his employer, 66-year-old Dan Triplett, who ran a septic tank installation business and gave differing accounts about Mack’s disappearance.

Surveillance footage shows both men arriving at a Mulhall work site in Triplett’s vehicle on September 20, and only Triplett leaving. Video also captured Mack entering the hole dug for a septic tank and never reappearing. Investigators excavated the site on October 21 and found Mack’s body buried about eight feet beneath the tank; an autopsy showed he had been shot in the back.

Triplett was arrested and charged with first-degree murder and desecration of a human corpse. He argued self-defense at trial, claiming Mack pulled a gun during an argument in the hole; a jury rejected that claim and convicted him. Anyone who knew Brent, his movements that week, or who has information about the Mulhall work site is asked to come forward.