'Young and the Restless' Star Kristoff St. John Dies at 52

"It is with unbelievable sadness that we say goodbye to our friend," reads a message shared by the Daytime Emmy Awards Twitter account.

Young and the Restless star Kristoff St. John was found dead inside his home on Sunday.

"It is with unbelievable sadness that we say goodbye to our friend, #DaytimeEmmys winner @kristoffstjohn1. @YandR_CBS RIP," reads a message shared by the Daytime Emmy Awards Twitter account.

Via social media, St. John's fiancee, model Kseniya Mikhaleva, mourned his death.

"How did it happen ??? How ??? Why did you leave so early ???? and left me alone ..... I can't believe you were everything to me .... you were a loving father, a loving man,.... how lovee?? we should doing a lot of things in future......," she wrote along with a photo of the couple together.

His cause of death is unclear.

In a joint statement, CBS Television Network and Sony Pictures Television said, "The news of Kristoff St. John's passing is heartbreaking. He was a very talented actor and an even better person. For those of us who were fortunate enough to work with him on The Young and the Restless for the last 27 years, he was a beloved friend whose smile and infectious laugh made every day on set a joy and made audiences love him. On behalf of the Y&R cast and crew, CBS and Sony Pictures Television, we offer our heartfelt sympathy to his family and loved ones, especially his two daughters, Paris and Lola."

Kate Linder, one of his Y&R castmates, shared her heartbreak.

"Kristoff St. John was such a kind man and a very dear friend to me and so many at Y&R. My late husband Ron and Kristoff just adored each other too. He will be missed terribly," she said via Twitter.

The actor won numerous awards for playing Neil Winters on Young and the Restless.

Authorities did not respond to a request for comment.

The Hollywood Reporter has reached out to his rep for more information.