Apparently from a drug overdose. This sucks...he's such an amazing actor. I hate that these amazing people get into that sort of stuff. These kinds of unexpected deaths are the worst...where you read it and have a minor emotional breakdown because it's so out of nowhere and you know you'll never see this person's work again.
I'm not gonna write up a cheesy obituary because I really hate them, but he was in amazing movies like "The Master", he played Truman Capote in "Capote", and generally just did amazing work. Even when he was in not-so-great films he was a highlight.
I wonder what they're going to do with the next two Hunger Games films now, since he died while filming it and his character is very important...ugh, what a horrible day. I'll miss him and all.