Diane Sawyer documentary examines Richard Simmons' mysterious seclusion

Emmy Award-winning journalist Diane Sawyer investigates the decade-long mystery behind fitness icon Richard Simmons' sudden disappearance from public life and his subsequent death in a documentary special that premiered Monday on ABC.

The special arrives as Southern California viewers who grew up watching Simmons remain curious about what drove the beloved personality into seclusion starting in 2014, and whether his story holds broader lessons about fame, isolation, and personal health.

Simmons rose to fame in the late 1970s and early 1980s through "The Richard Simmons Show," appearances on "General Hospital," and exercise videos including "Sweatin' to the Oldies," before vanishing from public view around 2014, according to ABC.

"He came with a great purpose, which was to reach out to everybody of all sizes," Sawyer said, according to ABC. "And somebody said, 'love them back to health.' And that was his mission, and it fueled him night and day."

Sawyer said Simmons sent her a large number of flowers before his death, each bearing a card that read "I trust you," and called to say he was ready to share his story. "It was the old Richard. And then, as we know, not long after, he died," she told interviewer Phillip Palmer, according to ABC.

After Simmons' death, his brother approached Sawyer and asked her to complete the project. She described the resulting film as "a mosaic," telling Palmer that interviews with family and associates gave her "tiles and pieces of the mosaic to put together who he was before he decided to go into hiding, who they think he was during it, and what might have happened if he had come back," according to ABC.

"You couldn't go anywhere without seeing Richard Simmons," Palmer said, according to ABC.

"The Mystery of Richard Simmons: A Diane Sawyer Special" premiered May 12 at 9 p.m. on ABC and is available on Disney+ and Hulu, the network said.

Sawyer described Simmons as someone who "lit up the room every time he arrived — surprised everybody," in remarks to ABC ahead of the premiere.