Duncan's rep told TMZ the actor never fully recovered from the myocardial infarction he suffered on July 13, but his death still came suddenly.
His fiancee, Omarosa Manigault, was with him in his L.A. hospital but had left for a short period of time. When she returned, he had died.
The rep added, "[Omarosa] Manigault is grateful for all of your prayers and asks for privacy at this time. Celebrations of his life, both private and public, will be announced at a later date."
Duncan received an Oscar nomination for Best Supporting Actor for his turn in "The Green Mile." His other films included “The Whole Nine Yards” and “Planet of the Apes.” He also appeared in several TV shows, most recently in the FOX show “The Finder.”
He worked as a bodyguard for celebrities like Will Smith, Martin Lawrence, Jamie Foxx, LL Cool J, and Notorious B.I.G. before he got his break.
Michael Clarke Duncan, best known for his role as John Coffey in "The Green Mile,” died on Monday. He was 54.