Heath Ledger's diary reveals extremes he took to play Joker in 'The Dark Knight'

Heath Ledger, who tragically died at age 28 from an accidental prescription drug overdose, left behind a production diary, where he developed ideas to portray Batman's nemesis Joker in 'The Dark Knight', it has been revealed.

The actor's production diary from 'The Dark Knight' was shown in German documentary series, 'Too Young to Die,' which chronicles Ledger's method exploration into the role of the Joker, the New York Daily News reported.

The last words scrawled in his production diary for the movie are as haunting as they are tragic.

He won an Academy Award for his unforgettable portrayal of the Joker.

Ledger's father, Kim Ledger, said that it was difficult to look through his late son's diary.

But as his production diary reveals, Ledger was also deeply troubled by what he learned while preparing for the villainous role.

"In order to inhabit his character, he locked himself up in a hotel room for weeks," the dad said.

He said that Ledger liked to dive into his characters, but this time he really took it up a notch.

The last words scrawled in the journal are, "BYE BYE."

Ledger finished the diary before production wrapped up.