An autopsy Wednesday is expected to reveal the cause of death for actor Heath Ledger. The 28-year-old father of one was found dead in his Manhattan apartment Tuesday. He was found by his housekeeper who had gone to Ledger's bedroom to let him know his masseuse had arrived for an appointment.

No suicide note, alcohol or other drugs were found in the luxury apartment where Ledger was found.

Ledger was shooting The Imaginarium of Doctor Parnassus with Terry Gilliam and had recently completed filming his role of The Joker in the latest installment of the Batman: Dark Knight .

Ledger told The New York Times in a November interview that he had trouble sleeping while portraying the Joker, whom he called a "psychopathic, mass-murdering, schizophrenic clown with zero empathy."

CNN correspondent Allan Chernoff told CTV's Canada on Wednesday that Ledger's portrayal of the role led him to seek out prescription medication.

"He had been taking sleeping pills and it's also believed he was taking some anti-anxiety pills as well. This role that he had recently acted in the Batman sequel, he really immersed himself and apparently it made him a little nuts in his head and he had some trouble sleeping," Chernoff said.

Ledger was one of Hollywood's brightest stars. He received an Academy Award(tm) nomination for his role in Brokeback Mountain, the same film that introduced him to Michelle Williams, with whom he fathered a daughter, Mathilda Rose.

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