Has anybody else heard that Heath Ledger's role as the joker may have been a part of his death?

I heard from somebody today that his death may have been somewhat related to his part as the joker...it was rumored that after filming was done he was still into character...i dont know if maybe it was he was on somthin wierd that made him think he was the joker or he was just messed up from the movie and thought he was the joker...i was just curious if anyone else heard that...and who else heard bout the dude in Michigan that got caught stealin batman posters and was dressed as the joker lol...loser