For many of his fans, Michael Jackson's death came as a shock.
But for those who followed his deteriorating health over the past two decades, the 50-year-old pop icon's demise may have been less of a surprise, rather the culmination of an assortment of health conditions -- including problems with stress and drugs -- that gradually whittled him down to a frail version of his former self.
Acquaintances have said in the past that Jackson was dealing with problems associated with his heavy use of the pain drug Demerol. And while details remain scarce, even before officials announced Jackson's death, the conditions behind his demise suggested a sudden and severe heart emergency.
"His personal physician who was with him at the time attempted to resuscitate my brother... as did the paramedics who transported him to Ronald Reagan UCLA Medical Center," Jackson's brother Jermaine Jackson said during a Thursday press conference. "At approximately 1:14 p.m., a team of doctors including emergency physicians and cardiologists attempted to resuscitate him for a period of more than one hour, and they were unsuccessful."
The true cause of Jackson's death will likely remain a mystery until the coroner's report becomes available. According to a statement form the Los Angeles County Coroner's Office, an autopsy will be performed today.
But those close to Jackson describe a hectic lifestyle.
"I think it was his lifestyle in general," said Stacy Brown, co-author of "Michael Jackson: Behind the Mask" and a family friend. "He had a lot of medical issues. Most of it was brought on by himself."
Kevin McLin, a friend of the family and Jackson's former publicist, agreed that the stress that Jackson put on himself lately led to burnout, which could have contributed to his demise.
"When you continue to try to sustain those kind of standards, you can really bring unwanted stress upon yourself," McLin said. "He had been working non-stop since he was 9 years old."
But Brown described another factor that may have contributed to Jackson's failing health.
"I think we will find that drugs played a major role, prescription and otherwise," Brown said. "From what I understand, there was even some heroin use. There was a lot of morphine. A lot of different drugs."
Jackson himself had admitted to a painkiller addiction in 1993. He claimed that his addiction stemmed from an injury he sustained in 1984, when a special effects explosion during the filming for a Pepsi commercial badly burned his head.
He also claimed that the mental stress of child-molestation allegations fueled his need for medicine.
"I was humiliated, embarrassed, hurt and suffering great pain in my heart," the pop star said in an audiotape statement in 1993. "I became increasingly more dependent to the painkillers to get me through the days of the tour. My friends and doctors advised me to seek professional guidance immediately in order to eliminate what has become an addiction."
Jackson also reportedly suffered from back pain -- a condition that took the spotlight during his much-publicized trial in 2005 for allegedly molesting a young boy. On March 10 of that year, Jackson failed to show up for a court appointment, ostensibly because his back pain became so severe that he had to go to the hospital instead.