He was discovered shortly after a parole hearing and it appeared he died of natural causes, the Department of Corrections and Community Supervision told CBS 2 News in New York.
Esposito was serving 15 years to life for abducting Beers and imprisoning her inside a soundproof underground room he crafted below his Long Island home. He was friendly with Beers and her dysfunctional family before the abduction.
Beers reacted to Esposito's death on Facebook, and invoked the name of another notorious kidnapper – Ariel Castro – who also died this week.
"I have to say that I'm not saddened by John's passing – I'm saddened for his remaining family – they lost John a long time ago, but now they've lost him forever," she wrote. "Within 24 hours, we have lost 2 monsters – Ariel Castro, who committed suicide; and John Esposito, who has died of unknown reasons."
Beers recently wrote a book about her ordeal, Buried Memories, and talked to PEOPLE earlier this year about her hellish experience at the hands of Esposito, as well as the sexual and physical abuse she suffered from family members prior to her abduction.
"You never fully recover," she said. "It's with me every day, but it's something I've learned to cope with."
According to Gothamist, Beers also revealed in her book that her co-author, WCBS 2 reporter Carolyn Gussoff, received a letter from Esposito in prison addressing his crime.
"I think Katie knows I will always wish her well. I'm sorry for what I’ve done," he wrote. "I'm sorry I even thought it up. It was a mistake."