Art Bell, the conspiracy theorist who was once one of the most popular radio hosts in the United States, has been found dead at his home in Nevada, local officials say. He was 72 years old.

Nye County Sheriff Sharon Wehrly confirmed in a brief statement that Bell was found dead on Friday at his home in Pahrump, which is a large town about 47 miles (76 kilometers) west of Las Vegas.

“He’s scheduled for an autopsy later this week to determine the cause of death,” Sheriff Wehrly said. Other details about Bell’s death were not immediately released.

Bell created the paranormal and conspiracy theory-themed radio show “Coast to Coast AM” in 1984 and hosted it for nearly 20 years. The 5-hour show was syndicated across the U.S. and Canada, receiving up to 10 million listeners a week.

The show was particularly popular among people working the night shift and those with an interest in UFOs and other paranormal beliefs. Bell’s proximity to Area 51 – the top-secret Air Force facility which is the subject of scores of conspiracy theories – added to his mystique.

Bell caused a scare among his listeners in 1998 when he abruptly announced his departure, telling the audience at the end of a show that his family had been affected by a “threatening, terrible event.” It prompted calls to police and wild speculation, ranging from a hoax to government threats or an alien abduction.

“I don’t want to sound too far-fetched, but what’s weird is that he always talked about government conspiracies and stuff, about high-tech secret stuff,” one listener told the Seattle Times in 1998. “I wondered if some of those secret organizations really do exist, and that Art was bringing up too many things on the air, and they told him to shut down or else.”

Bell returned to the airwaves about two weeks later, but the mystery endured for months. It later became clear that a close relative had been sexually assaulted by a teacher and his brief departure was caused by events stemming from that incident.

Health and family issues forced Bell to retire in 2002, although he continued to be an occasional guest host on the show. He hosted “Art Bell’s Dark Matter” on Sirius XM in 2013, but it abruptly ended less than two months later.