Prince had arranged to meet a doctor to try to kick an addiction to painkillers shortly before his death, it has been reported.
The late star's representatives called Dr Howard Kornfeld on April 20, the day before the musician died, to seek emergency help, attorney William Mauzy told the Minneapolis Star Tribune.
Mauzy, who is representing the Kornfeld family, said the doctor couldn't immediately meet Prince, so he sent his son Andrew on a flight from San Francisco that night to discuss treatment in a meeting planned for the next day.
Mauzy said it was Andrew Kornfeld who called 911 when Prince's unresponsive body was found in a lift at Paisley Park, the singer's suburban Minneapolis compound.
Mauzy and Howard Kornfeld have not responded to messages from journalists.
A law enforcement official has said that investigators are looking into whether the Purple Rain singer died from an overdose. They are also investigating whether the musician had suffered an overdose when his plane made an emergency landing in Illinois less than a week before he died.
Kornfeld runs Recovery Without Walls in Mill Valley, California. His website describes it as "specialising in innovative, evidence-based medical treatment for chronic pain and drug and alcohol addiction".
Mauzy told the newspaper that Prince's representatives called Kornfeld on the night of April 20 because the star "was dealing with a grave medical emergency".
Howard Kornfeld sent his son to explain how the confidential treatment would work, Mauzy said.
"The plan was to quickly evaluate his health and devise a treatment plan," Mauzy said. "The doctor was planning on a lifesaving mission."
Mauzy said Andrew Kornfeld arrived at Paisley Park at 9.30am on April 21 and was one of three people who found Prince's body. Mauzy said it was Kornfeld who called 911.
Authorities haven't released a cause of death. A post mortem was carried out the day after Prince's death but results, including toxicology results, aren't expected for up to four weeks.