(Reuters) - Music legend Prince died one day before he was scheduled to meet a doctor who specializes in addiction treatment for a “life-saving mission,” the doctor’s lawyer said at a news conference on Wednesday.

U.S. musician Prince performs at the Hop Farm Festival near Paddock Wood, southern England July 3, 2011. The body of music superstar Prince was found one day before a doctor was to meet him to help end an addiction to painkillers, the Minneapolis Star Tribune reported May 4, 2016, citing the doctor's lawyer. REUTERS/Olivia Harris/File Photo

California doctor Howard Kornfeld was first contacted by Prince representatives on April 20, one day before the singer’s body was discovered at his home, attorney William Mauzy told reporters.

“Dr. Kornfeld felt that his mission was a life-saving mission,” Mauzy said.

The news came shortly before federal authorities, including the Drug Enforcement Administration, announced they were joining the investigation into Prince’s death.

The cause of death remains undetermined, and it could be weeks before autopsy results are released. Police have said they found no signs of suicide or obvious trauma.

Kornfeld, who runs Recovery Without Walls, a clinic in Mill Valley, California, planned to fly to Minnesota to meet with Prince on April 22, Mauzy said. In the meantime, his son, Andrew Kornfeld, a staff member at his clinic, traveled to Minnesota on April 21 for an initial discussion.

When Andrew Kornfeld arrived at Paisley Park, the home-studio complex Prince owned in a Minneapolis suburb, the singer was not available, Mauzy said. A staff member found the artist unconscious in an elevator, and Kornfeld called 911.

Prescription opioid medication was found at the scene, according to a law enforcement source with knowledge of the investigation but not authorized to speak publicly.

Mauzy confirmed Andrew Kornfeld had opioid medication used to treat pain and addiction in his backpack, but emphasized that no drugs were given to Prince by the doctor or his son.

It was not immediately clear whether Kornfeld’s drugs were the same medication the law enforcement source said was found at the scene.

In a statement, the U.S. Attorney’s office in Minnesota said it would join the Carver County Sheriff’s ongoing probe into Prince’s death.

“The DEA and U.S. Attorney’s office are able to augment this local investigation with federal resources and expertise about prescription drug diversion,” the office said.

Mauzy expressed concern that Andrew Kornfeld could face charges, but said he believes he would have immunity with regard to the medication in his backpack under a Good Samaritan 911 law. The lawyer did not elaborate further on possible charges.

Andrew Kornfeld was interviewed by investigators from the sheriff’s office on April 21 and returned to California that night, Mauzy said.

Howard Kornfeld’s clinic specializes in medical treatment for chronic pain and drug and alcohol addiction, according to its website.

“Dr. Kornfeld was never able to meet Prince, never talked to Prince, and was sadly not able to arrive in time to help Prince,” Mauzy said.

Representatives for the late singer did not immediately respond to a request for comment.