It didn't surprise me one bit. I knew he had a substance abuse problem and that he recently went into detox a rehab.
Heroin addicts are more vulnerable to overdoeses when they're clean. ( Although I don't know if this was the case )
Its how Sid Vicious died.
They detox and get clean and then come out and do the same amount they did when they were using and it kills them.
I liked him in The Big Lebowski as Brent....hillarious.