St. John had played the character of Neil Winters since 1991 on the long-running CBS daytime soap opera. The actor was nominated nine times for Daytime Emmy Awards, and he won 10 NAACP Image Awards.
St. John was set to be wed, announcing in September that he was engaged to model Kseniya Mikhaleva. He posted a photo of the engagement ring with the caption “She said yes.”
Actress Yvette Nicole Brown reacted to the news of his death Monday on social media, mourning her fellow actor friend.
The Daytime Emmy Awards also tweeted out condolences: “It is with unbelievable sadness that we say goodbye to our friend, #DaytimeEmmys winner @kristoffstjohn1”