Dude, they found sleeping pills beside him. He was sick and combating pneumonia. The death was accidental (The autopsy proved inconclusive so that we don't know for sure what killed him) according to his family.
I heard he spent a month alone to get ready for the Joker part. He was having sleep problems because of it and he took sleeping pills. It was either a suicide, or an accidental OD. Although could be something else, they haven't done an autopsy.
It's sad. He was a good actor, even hough I am against BBM.
Yes, they have done an autopsy. They did one today, this afternoon. The results were inconclusive, and they need to do more toxicology testing first before they can come to a definite answer as to how he died.