MTV issued a statement saying it was shocked and saddened to learn of its star's death.
"We are waiting for more information but at this time, our main concern is for the Gandee family and their friends," the network said. "Our thoughts and prayers are with them. Shain had a magnetic personality, with a passion for life that touched everyone he met and we will miss him dearly."
A neighbor, Swanna Frampton, said she had known Shain Gandee since he was a small child.
"He loved to live and have fun. He was a great person," Frampton said. "He did what (the show) wanted him to do, but he wasn't like that. He was a real person. If you needed help, if needed something, he would come help you no matter what."
Shooting for the second season of "BUCKWILD" had begun, but MTV spokesman Jake Urbanski said Monday afternoon it has been suspended. He had no further details.
MTV said the half-hour series in the old "Jersey Shore" time slot was pulling in an average of 3 million viewers per episode since its premiere and was the No. 1 original cable series on Thursday nights among 12- to 34-year-olds.
Shain Gandee is the third BUCKWILD cast member to make headlines.
Last week, 24-year-old Salwa Amin was sent back to jail for violating the terms of her bond following a February arrest. She was charged with two counts of drug possession with intent to deliver and initially jailed on $200,000 bond. That was later reduced to $100,000, but Amin remained behind bars without bond on Monday.
State Police say a multi-agency task force arrested Amin and two other people at a Summersville residence after receiving a tip from an informant. A search found oxycodone pills, heroin and $3,000 in cash.