Jackson is believed to have died from cardiac arrest and law enforcement sources told ABC News Jackson was heavily addicted to Oxycontin and received it and Demerol in daily doses.
Deepak Chopra, a spiritual author, medical doctor and Jackson's friend, told "Good Morning America" the famed singer asked him for the prescription drug Oxycontin after his trial in 2005, saying that he was in pain.
"That's when I became suspicious that something was going on, that he was dependent," Chopra said, adding that Jackson tried to avoid talking about the subject with him. "Michael was addicted, but he had enabling doctors who perpetuated his addiction and actually started it."
Rev. Jesse Jackson, who spent Friday with the Jacksons, spoke to ABC News about their concerns about Dr. Murray and his role in Michael's final hours.
Rev. Jackson confirmed that the family is suspicious.
The doctor's behavior in their son's final moments didn't sit right with the Jacksons, according to Rev. Jackson.
"When did the doctor come? What did he do? Did he inject him? If so, with what?" Rev. Jackson asked. "Was he on the scene twice? Before and then reaction to? Did he use the Demerol? It's a very powerful drug. Was he injected once? Was he injected twice?"
The 911 audio tapes released Friday confirmed that a doctor was present in the room.
In the urgent, but collected phone call, an unidentified man described Jackson as lying on a bed unresponsive while a doctor kept "pumping him."
"I have a personal doctor here, but he's not responding to anything, CPR, or anything," the caller said, referring to Jackson only as "a gentleman here that needs help and he's not breathing yet."
ABC News has learned that Los Angeles police were told Jackson received an injection of the painkiller Demerol an hour before the 911 call was placed.
Rev. Jackson also said the family is considering and will "probably" order a second independent autopsy.
Los Angeles Police Deputy Chief Charlie Beck said Friday in a press conference that the robbery/homicide division has been in contact with Dr. Murray and would be interviewing him soon.
Police said interviewing the attending physician was a standard part of the investigation.
"A doctor has yet to sign to the Jackson death certificate," said LAPD spokesman Richard French. "Part of the investigation involves interviewing the attending physician."
Police believe Dr. Murray could provide a critical clue in determining what killed Michael Jackson.
Cops impounded a silver BMW from outside Jackson's Los Angeles home, which is registered to a Susan Mary Rush who is Murray's sister.
Law enforcement officials say the reason the car was towed is because it may contain medication or evidence that could assist the coroner. But officials dismissed rumors that Murray has avoided answering questions.
"Robbery homicide division detectives have been in contact with the physician and his representatives and have scheduled an interview which will take place shortly," Los Angeles Police Department Deputy Chief Charlie Beck said Friday. "We do not consider him to be uncooperative at this time."
In 2007, Jackson settled a lawsuit with a Beverly Hills pharmacy that claimed Jackson owed them more than $100,000 for prescription drugs, and during a search of his Neverland estate, the district attorney said syringes and Demerol were found on the property.
Jackson's autopsy on Friday lasted three hours but its results will not be known for weeks.