The most common is when a vehicle is left running in a closed garage. It also happens during harsh winter weather when a person is waiting inside the vehicle for it to warm up or waiting for the windows to defrost and neglects to make sure the tail pipe is clear.
She said fumes would build up in the vehicle in both cases. In garages, it's best to open the door because a cracked window would not suffice. In winter weather, people should always check to make sure the tail pipe is not obstructed by snow or ice.
Authorities used a bulldozer to pull the Bronco from the mud. The bodies were taken to the state Medical Examiner's Office.
Humphreys said because the incident is considered accidental, he didn't anticipate any further information being released by the sheriff's office.
Shain spent Saturday with family friends and fans at the grand opening of his cousin's general store in Ohio.
Lewis had just opened Gandee's General Store in Crown City, Ohio, where she sells the now famous Gandee Candy and other items. She said Shain came out Saturday to support her and the business and meet with fans.
She said he seemed to have a good time interacting with fans that day.
"He was doing burnouts in the road and giving people hugs and stopping to talk to everyone," Lewis said. "These were full-fledged conversations, not just 'hi' and 'bye,' but full-fledged conversations."
She said fans approached him all day with items to autograph and he turned no one away, signing T-shirts, cellphone cases and even one man's pickup truck.
She said fans from around the world have contacted her by phone and via Facebook to show concern and support. Fans spoke online Monday evening of wearing camouflage clothing Tuesday in memory of Shain. People sent her messages all day to tell her they had their camo on.
Lewis said success hadn't changed Shain.
"He didn't change anything for the cameras," Lewis said. "He was who he was and he loved his life."
The cousins didn't grow up together, but she said they hung around together at family reunions over the last five years. She said he was just the same as he always had been and the newfound fame meant nothing to him.
"He died doing what he loved, he died muddin'," she said.
Lewis and others have organized a mud run in Ohio to raise money for funeral expenses. Participants are asked to meet at the Kroger store in Proctorville, Ohio, at 4:30 p.m. today. Donations will be accepted. More information is available on the Gandee's General Store Facebook page.
She did not know of any fundraiser plans or events in the Sissonville area.
Funeral arrangements had not been finalized Tuesday.
Contact writer Ashley B. Craig at ashley.cr...@dailymail.com or 304-348-4850.