Ledger preferred the quieter borough of Brooklyn, where he and Williams lived for two years, to his apartment in Manhattan's trendy SoHo neighborhood (above). Photo by: James Devaney / WireImage
Heath Ledger: 1979 - 2008| Heath Ledger
A police source confirmed to PEOPLE that two packets of prescription pills were found near the body and that "apparently one was a sleeping type of medication" – most likely something similar to Ambien, which Ledger was known to be taking. "They're doing toxicology reports," says a source close to Ledger's family, who adds that the actor was suffering from pneumonia at the time of his death. "The family has been told there's no reason to think it's anything but accidental." Ledger's father, Kim Ledger, called the death a "very tragic, untimely and accidental passing" and said his son "was found peacefully asleep in his apartment." The actress Michelle Williams, who lived with Ledger for more than two years and is Matilda's mother, was with her daughter and working on a movie in Sweden when she got news of his death. Says a close friend: "Michelle is devastated."

An intense, restless man known as much for his partying and wild streak as for his sweetness and sensitivity, Ledger had been having problems sleeping, particularly since signing on to play the role of the Joker in Chris Nolan's upcoming Batman epic The Dark Knight. He spent much of last year filming in Chicago and London and by all accounts sank deeply into the character, which he described to The New York Times as "a psychopathic, mass-murdering, schizophrenic clown with zero empathy." In November he told a Times reporter how Ambien barely worked for him. "Last week I probably slept an average of two hours a night," he said. "I couldn't stop thinking. My body was exhausted and my mind was still going."

On top of that, several sources told PEOPLE, Ledger never fully recovered from his split with Williams, with whom he fell in love while making his breakout movie, 2005's Brokeback Mountain. They had shunned Hollywood for an idyllic stroller-and-Starbucks life on the streets of Brooklyn, blending in as best as their fame allowed. But since their split Ledger had become a fixture on New York City's party circuit, spending nights in clubs and restaurants and, say witnesses, drinking and taking drugs to excess. Just two days before he died he was spotted at the trendy Beatrice Inn in Manhattan, drinking into the night. "He was in a ski mask with holes cut out at the eyes and mouth and a hood over his head," says one clubgoer. Says a friend: "Heath partied a lot. He didn't really stop partying. At nights when I was going home, he was just starting. Still, he looked like he lived a really happy life. Everyone knows he did a lot of drugs, but he always had it under control."