Actually, it isn't drugs. They have said that it was sleeping pills.
You see, he was doing a new movie that will come out this year or next year. A Batman Movie. He was playing the joker and he only got 2 hours sleep a night because he was working so hard and overtime. So, he relied on the pills to help him. It has been said by the News that test results for the pills is being done, but we won't know until a week plus. It's a big mystery.
I would love to see 10 Things I Hate About You. I love him in the A Knight's Tale. I really think he was going to be one of the best. It's just a tragdity. I really cannot believe it.