LOS ANGELES — Michael Clarke Duncan was one big, irresistible jumble of contradictions.

His presence was formidable, even intimidating: The former bodyguard had a muscular, 6-foot-4 frame, but it was topped by the brightest of megawatt smiles.

The prolific character actor, whose dozens of movies included an Oscar-nominated performance as a death row inmate in “The Green Mile,” died Monday at age 54. Duncan died at Cedars-Sinai Medical Center in Los Angeles, where he was being treated for a heart attack, said his fiancée, reality TV personality Rev. Omarosa Manigault, in a statement.

Tom Hanks, star of 1999’s “The Green Mile,” said he was “terribly saddened at the loss of Big Mike. He was the treasure we all discovered on the set of ‘The Green Mile.’ He was magic. He was a big love of man and his passing leaves us stunned.”