Heath Ledger :Batman Dark knight?

ok...so what are some facts about him? like do you think the movie character really got into his mind? and that kinda led to his unfortunate death? Do you think if he would have never did the film he would have still been with us today? Also I heard had to be in a hotel room by himself to get into character...what do you think went on there? do you think he went a lil crazy himself? thank you