Michael Clarke Duncan, the prolific character actor whose dozens of films included an Oscar-nominated performance as a death row inmate in The Green Mile, has died aged 54 Associated Press in Los Angeles reported this morning.

Duncan died yesterday at the Cedars-Sinai medical centre in Los Angeles, where he was being treated for a heart attack, according to his fiancee, Omarosa Manigault.

The muscular, 6ft 4in Duncan – a former bodyguard who turned to acting in his 30s – "suffered a myocardial infarction on 13 July and never fully recovered", said a statement issued by a spokesman.

Duncan had a handful of minor roles before The Green Mile brought him an Oscar nomination for best supporting actor. The 1999 film, based on the Stephen King novel of the same name, starred Tom Hanks as a guard at a prison in the 1930s. Duncan played John Coffey, a convicted murderer with a surprisingly gentle demeanour and extraordinary healing powers. He's performance impressed critics and moviegoers and he quickly became a favourite in Hollywood, appearing in several films a year.

He owed some of his good fortune to Bruce Willis, who recommended Duncan for The Green Mile after the two appeared together in Armageddon. Duncan would work with Willis again in Breakfast of Champions, The Whole Nine Yards and Sin City.

Some of his other films includes the superhero film Daredevil and comedies including Talladega Nights and School for Scoundrels.

His deep baritone voice alone was good enough for several animated movies, including Kung Fu Panda, Delgo and Brother Bear.

Duncan was born in Chicago in 1957 and raised by a single mother whose resistance to his playing football led to his deciding that he wanted to become an actor. But when his mother became ill, he dropped out of college and worked as a ditch digger and bouncer to support her. By his mid-20s, he was working as a bodyguard for Will Smith, Jamie Foxx and other stars in Los Angeles.

He decided to quit that line of work – and pursue acting full-time – after the murder of rapper Notorious BIG, whom Duncan had been hired to protect before switching assignments.