Shain Gandee died doing what he loved.

While mudding with his uncle, David Gandee, and friend, Donald Robert Myers, following a night at a West Virginia bar on Saturday, the "Buckwild" star's 1984 Ford Bronco got stuck in the thick, dirty water and its tailpipe submerged, thus preventing the exhaust from leaving the car.

On Tuesday, the Kanawha County Sheriff's Department in West Virginia announced that completed autopsies confirmed: "The manner of death is accidental and the cause was carbon monoxide poisoning for all three subjects."

[Related: Shain Gandee Dead at 21: Who Was the 'Buckwild' Star?]

When Shain's truck was discovered early Monday morning, "The vehicle sat unevenly, but upright, and was partially submerged in deep mud," according to a statement from officials in Kanawha County, which led to speculation that carbon monoxide was to blame. "Mud was covering the lower part of the passenger side door of the vehicle, but the driver's side of the vehicle was above the mud. The muffler of the vehicle was completely below the surface of the mud."

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In the wake of the shocking deaths, Shain’s family and friends are grieving the fun-loving 21-year-old, who was the breakout star of the MTV reality series. On Tuesday, his second cousin Ashely Gandee Lewis updated fans on Facebook. "I just wanted to let everyone know that the family feels that Shain died peacefully in his sleep without pain or suffering," she wrote. "That it probably was carbon monoxide. They are making arrangement now for his funeral. Nothing is confirmed but they are thinking Saturday. So private or public hasnt been decided I will try to keep everyone updated."

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Despite Shain's fame since "Buckwild's" premiere in January, he did not have much money and his family is struggling to pay for his funeral. So they are planning to both raise funds and honor their beloved with a "mud run" on Wednesday in Proctorville, Ohio, which is not far from Charleston, West Virginia, where the show is filmed. For $10 per vehicle, participants can take part in the off-road event, which was one of his favorite pastimes.

Ashley Gandee Lewis will also be accepting donations at her Crown City, Ohio, general store, where the reality star made an appearance on Saturday for the grand opening. "We actually had people here from Texas, from Dayton, Ohio, from Pennsylvania," she told Radar Online. "People drove hundreds of miles just to meet him because he was such a lovable guy."

[Related: MTV Shuts Down 'Buckwild' Production]

With the death of Shain and the recent arrests of fellow "Buckwild" castmates Salwa Amin for heroin and oxycodone possession and Michael Burford for DUI, the future of the controversial MTV reality series is uncertain. Following Monday's tragedy, production on the upcoming second season was halted. And if the mayor of Charleston had his way, it would never return to TV again.

"Of the few cast members on the show already, two have had legal issues and now one has died," Danny Jones tells TMZ. "The show only enhances the negative stereotype the Kanawha Valley already has. I hope the show's life is short."

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