Theron later offered her condolences as well: "It's really, really sad. I hope his family is OK. I wish them the best,'' according to Entertainment Tonight's Web site.
Hollywood starlet Lindsay Lohan broke down in tears upon hearing the news while at lunch with friends DJ AM and Samantha Ronson, according to TMZ. Lohan ran with Ledger on the party circuit, and their friendship led to rumors of a romance between the two last fall.
New Zealand actor Sam Neill responded in disbelief upon hearing news of the actor's fate, according to the Australian Herald Sun. Neill said, "Like many in the acting community, I am tremendously saddened and shocked by Heath's death.
"Whatever the circumstances, Heath was someone who had everything to live for. He was a very nice man, and a phenomenal screen actor. This is unbelievable."
Ledger's "Ned Kelly" costar, actor Joel Edgerton, was shattered, according to the Australian Herald Sun and spoke of how the actor was meant for "bigger and better things."
Ledger, with actor Orlando Bloom, in a poster for 2002's "Ned Kelly," during which Edgerton worked with the late actor.
"Heath was an exceptional human being with a massive heart: always generous, adventurous and impressive," Edgerton said, according to the Australian Herald Sun.
"I always believed, as a young man, he was wise well beyond his years. And as far as his work goes, I know I'm not alone in thinking he was just getting started to realize an incredible potential.
"My heart goes out to those who knew him best: to his family, to Michelle and Matilda, and to his friends, especially his Perth gang who I know will be heartbroken right now. Those friends and his family were everything. It really is a sad day. An incredible shock."
Australian actor Guy Pearce had never met Ledger but offered his sympathies to the "friend I never got to meet," according to Australian papers. He said, "Mate, I had such admiration for you. Your dignity, humility, grace and talent will always be an inspiration to me."
Ledger recently finished filming his role as the Joker in "The Dark Knight," which Warner Bros. Studios was planning on releasing next summer.
Warner Bros. Studios released the following statement:
"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. Our hearts go out to his family and friends."
The Ledger family spoke in Perth, Australia (Ledger's birthtown), and released the following statement:
"We, Heath's family, confirm, the very tragic, untimely and accidental passing of our dearly loved son, brother and doting father of Matilda. He was found peacefully asleep in his New York apartment by his housekeeper at 3:30 p.m. U.S. time.
"We would like to thank our friends and everyone around the world for their well wishes and kind thoughts at this time. Heath has touched so many people on so many different levels during his short life but few had the pleasure of truly knowing him.
"He was a down to earth, generous, kind-hearted, life-loving and selfless individual who was extremely inspirational to many," the Ledger family's statement read. "Please now respect our families need to grieve and come to terms with our loss privately."