TRAGIC: OSCAR WINNER PHILIP SEYMOUR HOFFMAN DIED OF HEROINE OVERDOSE

Tragic Oscar winner Philip Seymour Hoffman had separated from his longtime girlfriend Mimi O'Donnell in the months leading up to his death, it can be revealed.

The 46-year-old, who has three elementary-age children with the costume designer, also 46, began renting a $10,000-a-month apartment in Bethune Street in Manhattan's Greenwich Village in October.

And it was here his body was found Sunday morning by close friend and playwright David Bar Katz, who had been asked to check up on him by Miss O'Donnell. The actor's estranged partner was later seen weeping as she entered the property.

Sunday afternoon, a New York Police Department source told MailOnline: 'It is my understanding that Mr Hoffman and his girlfriend were separated.'

Father-of-three: The 46-year-old, had three elementary-age children with the costume designer, Cooper, 10, left, Tallulah, 7, and Willa, 5

The body of Philip Seymour Hoffman was removed from his apartment building just before 7 p.m. Sunday after he was reported dead

Seymour Hoffman and Mimi O'Donnell, pictured with their son Cooper in December 2013 in New York, had split recently

Philip Seymour Hoffman enjoyed an afternoon stroll with his partner Mimi O'Donnell in New York, in June after he returned from his stint in rehab

Authorities confirmed that the last time the stage and film actor was seen was around 8 p.m. on Saturday.

The Office of the Chief Medical Examiner is yet to determine the exact cause of death, but law enforcement sources revealed a drug overdose was to blame. Officers found a charred spoon in the kitchen sink, police sources told the New York Post.

A relative told The Post: 'We're just really devastated that this could happen.'

'There had always been a concern with the business he was in,' said Doris Barr, 76, whose son is married to Mr Hoffman's sister.

After Mr Katz called 911, emergency workers rushed to the scene where Mr Hoffman was declared dead on arrival.

Just before 7 p.m., after CSU investigators, wearing white plastic suits, spent the entire afternoon and much of the evening going in and out of Mr Hoffman's apartment, the crime scene van moved to make way for the medical examiners wagon to pull up to the building.

A breakthrough role came as a gay member of a porno film crew in 'Boogie Nights,' one of several movies directed by Paul Thomas Anderson that he would eventually appear in.

He often played comic, slightly off-kilter roles in movies like 'Along Came Polly,' 'The Big Lebowski' and 'Almost Famous.'

Just weeks ago, Showtime announced Mr Hoffman would star in 'Happyish,' a new comedy series about a middle-aged man's pursuit of happiness.