CHARLIZE THERON, GEOFFREY RUSH, DENNIS HOPPER and other stars speak out as Hollywood mourns the loss of HEATH LEDGER, who died Tuesday. He was 28.

HELENA CHRISTENSEN, once rumored to be Heath's girlfriend, told Women's Wear Daily she was on her way to see him yesterday when she heard the news: "He was a sweet, smart and talented young man and had many friends. My heart goes out to his family. I am just beyond sad at this point, and shocked ... I was on my way over to pay him a visit when I found out. I had just left him a message and heard his voice on the machine ... He was such a special and genuine person, so extraordinarily talented because he was so raw and honest with his feelings. He was so full of life, so electric ... This is immensely sad."

Oscar winner GEOFFREY RUSH, who co-starred with Heath in the 2006 film 'Candy,' called the 28-year-old's passing "such a sad event. I admired Heath enormously. He was a sensitive and committed and daring actor. This is truly a tragedy. I send my condolences to his family and friends and colleagues."

JOHN TRAVOLTA told ET: "I am devastated. I loved Heath. He is probably my favorite actor. I don't like what has happened at all, so I am very sad about it."

When asked for her reaction, fellow Aussie NICOLE KIDMAN said, "What a tragedy. My heart goes out to his family."

Adding her sympathy for his family was CHARLIZE THERON, who told ET: "It's really, really sad. I hope his family is okay. I wish them the best."

In speculating on the cause of Ledger's death, DENNIS HOPPER told ET: "That's terrible. Drugs today ... when we stopped taking drugs, they started. It is just an epidemic. I am sorry to hear that. He was a great talent."

MEL GIBSON commented: "I had such great hope for him. He was just taking off and to lose his life at such a young age is a tragic loss. My thoughts and prayers are with him and his family."

Heath will star posthumously as "The Joker" in Warner Bros.' 'The Dark Knight,' the new Batman movie coming out this summer. The following statement was issued by ALAN HORN, President & COO, Warner Bros. and JEFF ROBINOV, President, Warner Bros. Pictures Group: "The studio 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."

Heath recently portrayed BOB DYLAN in the imaginative biopic 'I'm Not There,' and director TODD HAYNES says, "This is an unimaginable tragedy. Heath was a true artist, a deeply sensitive man, an explorer, gifted and wise beyond his years. There is no finer person on this earth." The film's producer, CHRISTINE VACHON, adds, "My heart breaks for Heath's family. Heath was a wonderful artist and a lovely man."