No cause had been determined (as of Tuesday night) although some say it was a suicide, and others speculate that it could have been connected to the work he's done to prepare for and act the part of The Joker in "The Dark Knight," the newest Batman film, due in theaters in July.
I got this info from Wikipedia:
"*He described the character as a 'psychopathic, mass murdering, schizophrenic clown with zero empathy' *To prepare for the role, Ledger lived alone in a hotel room for a month, formulating the character's posture, voice and psychology. *While he initially found it difficult, Ledger was eventually able to generate a voice... He started a diary, in which he wrote the Joker's thoughts and feelings to guide himself during his performance. *He was also given Batman: The Killing Joke and Arkham Asylum: A Serious House on Serious Earth to read, which he "really tried to read [...] and put it down". *Ledger also cited inspiration in A Clockwork Orange and Sid Vicious. *The challenge of the role put a strain on Ledger's sleep patterns, finding himself unable to rest for more than a few hours each night."
I don't know, but I would say it's quite a coincidence that they found him by a bunch of sleeping pills, even though they don't know if he took any until toxicology reports come back. I also heard he may have had pneumonia at the time of his death.
For whatever reason he died, I feel like Hollywood has lost one of its more promising young actors. After getting stuck in "teen heartthrob" roles after his work in "Ten Things I Hate About You," he landed a serious role as Mel Gibson's son in "The Patriot." He did several movies after that, but I felt really showed his stuff playing a cowboy that falls in love with Jake Gyllenhaal's character in "Brokeback Mountain." (He may have even been nominated for an Academy Award for the movie, I'm not sure.) After that, I looked at him with much more respect as an actor.
I then fell in love with him again when he played Jacob Grimm alongside Matt Damon in "The Brothers Grimm." He was so freakin' cute!!!
I haven't seen a whole lot of his movies besides those, but I want to. Other films of his I would like to see include "I'm Not There," about Bob Dylan, and "The Dark Knight." It will be wierd to see him in the performance that may have altered the way he looked at the world... at least his last performance. But I'll bet it's a good (and scary) one. Hell, I already think it's scary and I've only seen pictures and previews (see above for a pic).
He was in the middle of filming another movie when he died, but I don't know much about it and I'd be willing to bet they do some recasting after this tragedy.
Anyway, R.I.P. Heath.
It's always sad when someone young dies, especially if they show as much promise as this guy.
(disclaimer: this information comes from a mixture of news stories, rumors and internet chatter. I cannot confirm any of it personally. also included here are my opinions about his work, since i respect what he's done)