'The Dark Knight' Turns 10: How the Joker Took a Toll on Heath Ledger Before His Death at 28

Ten years ago, anticipation was astronomically high for Christopher Nolan’s sequel to Batman Begins,The Dark Knight. It wasn’t just another comic book spectacle — it was the first movie to star Heath Ledger since the actor’s shocking death at 28.

In early 2008, months before The Dark Knight opened on July 18, an exhausted Ledger retreated to his New York City apartment to try and get some rest and recuperate from an illness he couldn’t shake.

Despite warnings from friends and family about mixing sleeping pills with prescription medications, the Brokeback Mountain star was found dead on January 22, 2008 in his apartment. A toxicology report revealed a fatal mix of prescription drugs in his system.

Years after his death, PEOPLE spoke with those closest to him about his amazing life and untimely death. They described a young superstar and father grappling with the pressures of fame, reeling from a recent breakup — and struggling in his final weeks.

Gerry Grennell, Ledger’s friend and dialect coach who lived and worked with the star while he was shooting The Imaginarium of Doctor Parnassus in the final weeks of his life, spoke with PEOPLE in 2017 for a cover story on Ledger, nine years after the actor’s death. He recalled his friend being “exhausted, emotionally and physically” while battling a lingering pneumonia-type illness.

Ledger took sleeping pills, but a good night’s rest eluded him, particularly since playing The Joker in The Dark Knight, a character he described to The New York Times as a “a psychopathic, mass-murdering, schizophrenic clown with zero empathy.”

During the making of the film, Ledger shared that he only slept “an average of two hours a night.” “I couldn’t stop thinking,” he told the Times. “My body was exhausted, and my mind was still going.”

He would go on to posthumously win a best supporting actor Oscar for his performance in 2009 after his death.

Grennell said the Ledger’s mood remained low after wrapping on The Dark Knight. “He missed his girl, he missed his family, he missed his little girl — he desperately wanted to see her and hold her and play with her,” he added, referring to Ledger’s former girlfriend Michelle Williams and their then-2-year-old daughter, Matilda. “He was desperately unhappy, desperately sad.”

Ledger and Williams met on the set of Brokeback Mountain, for which they received Oscar nominations. Their daughter, Matilda Rose, was born in 2005.

“Heath loved Matilda so much,” his longtime friend, hip-hop artist N’fa Forster-Jones told PEOPLE in 2017. “That perspective of what matters was apparent. It’s a big shift for a young man, or young anyone, who goes from being their own person to being a parent. He saw as his little buddy, his star, his future, his better self. He just loved Matilda so much. So much.”

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But in his final weeks, Grennell said Ledger knew he was spiraling. Still, he couldn’t stop himself from taking the pills. “He said, ‘I got to stop, it’s not helping, I’m not well, it’s making me feel more upset,’” Grennell continued. “It wasn’t helping with the relationship issues, it wasn’t helping with missing his kid, it wasn’t helping his sleeping — and he knew that.”

Despite his love of acting, the Australia native was never interested in fame and the type of attention it brings. “I don’t remember him thinking any of it was fun … Maybe having money, financial freedom, and the pick of the worlds finest women was awesome, but the other side of it was grotesque,” said Forster-Jones.

“Being such a social guy, having to be a bit of a hermit, or wear hats and glasses was super annoying,” he added, describing the lengths to which Ledger went to avoid the paparazzi. “His happiest I remember was times like when we were in Bondi on the beach catching waves, and nobody really looking his way, and when he moved to Brooklyn and could walk around with nobody bothering him.”

Part of the problem, according to Forster-Jones, was dealing with the high expectations others had set for him. “I think everyone expected too much from him, as though they got use to it, and as though he was indestructible. Sometimes to the point that he suffered too much for it.”

Djimon Hounsou, his costar in 2002’s The Four Feathers, revealed in the 2017 documentary I Am Heath Ledger that he was taken aback when he saw Ledger not long before his death.

“I ran into him in New York, hadn’t seen him for a couple of years, and [thought], ‘Wow, Heath has this change.’ But the way he has changed kind of got me a little concerned, you know. And I looked at him, I thought, ‘Wow,’ with a bit of a concern, you know?” he said.

While friends and colleagues sensed his desperation, sister Kate Ledger — who often spoke to her famous brother three times a day — told PEOPLE in 2017 that he remained a “happy boy” with her and other family members, and did not project “doom and gloom” in his final weeks.

At the same time, she knew her brother was “struggling” with an illness, and warned him to be careful with his medications a few weeks before his death.

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“I just said, ‘You’ve got to be very careful mixing things,’ and he was like, ‘Katie, hello, come on, of course,’” she said.

Kate described their final phone conversation just before his death as upbeat.

“I was cooking dinner … and we were laughing. Then he said, ‘I’ve got to go, and I’ll call you at 8:30 in the morning’ and that was it,” she recalled. “That was our last conversation. I said ‘Okay, I love you.’ And that was it. It’s heartbreaking.”

With reporting by Liz McNeil