Heath Ledger was told to seek professional help for his personal problems while filming 'The Dark Knight'.

The late Australian actor - who tragically died from an accidental prescription drugs overdose in January - was reportedly warned he had become too obsessed with his portrayal of iconic Batman villain The Joker in the upcoming blockbuster.

A source told FOX News: "Heath refused to talk to anyone out of character. If you tried to communicate with him normally instead of The Joker, he would just ignore you."

"He would often come to the set to hang out even on his days off, freaking everyone out. Towards the end of filming, he was warned by people that he had gone too far, but it was almost like he couldn't connect with those who cared for him anymore."

Ledger reportedly locked himself in an apartment for an entire month before playing The Joker, who he described as a "psychotic, mass-murdering clown."

Ledger also admitted he had such trouble sleeping while shooting the film he resorted to taking the prescription drug Ambien.

Sources on the set of 'The Imaginarium of Doctor Parnassus' - the movie Ledger was filming when he died - also claimed the actor could not "snap out" of character and seemed to have "lost sense" of who he was.

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