Leading figures in Hollywood Wednesday continued to mourn the sudden death of Heath Ledger, a rising star who was hailed as one of the great hopes among his generation of actors and got an Oscar nomination for his role in the 2005 film "Brokeback Mountain."

The 28-year-old Australia native was found dead Tuesday afternoon in his apartment in the Soho area of New York. A cause of death was not yet determined, although some media reports from New York indicated that Ledger was found by a masseuse, and sleeping pills were scattered on the floor.

"I had such great hope for him," said actor and filmmaker Mel Gibson, who portrayed Ledger's father in the 2000 film "The Patriot." "He was just taking off, and to lose his life at such a young age is a tragic loss."

Ledger was nominated for the best actor Oscar in 2006 for his work in Ang Lee's "Brokeback Mountain," which followed the complex and tortured 20-year romance of a ranch hand and a rodeo cowboy.

In a statement released to the entertainment news program "Extra," Australian actress Nicole Kidman said, "What a tragedy. My heart goes out to his family."

Hollywood film historian and author Leonard Maltin said, "I admired him so much ... his work was so good."

"From the beginning when it seemed he might just be another good-looking young guy who came up here from Australia, he worked film by film, year by year, to prove he was more than that," Maltin told local TV channel CBS2.

Ledger first gained fame appearing in the teen comedy-romance " 10 Things I Hate About You," but went on to appear in increasingly demanding roles in films such as "The Patriot," "A Knight's Tale," "Monster's Ball" and "The Order."

He most recently appeared in the Bob Dylan homage film "I'm Not There," for which co-star Cate Blanchett has received an Oscar nomination.

He will be seen later this year in "The Dark Knight," portraying the Joker in the sequel to "Batman Begins."

Warner Bros., which is producing "The Dark Knight," issued a statement Tuesday saying that the company "is stunned and devastated by this tragic news."

"The entertainment community has lost an enormous talent. Heath was a brilliant actor and an exceptional person. Our hearts go out to his family and friends," said the statement.