Documents unsealed Monday in the Prince death investigation pull back the curtain, ever so slightly, on law enforcement's response in the days after the musician's lifeless body was found inside a Paisley Park elevator.

But the search for answers into who is responsible for his overdose death continues as the anniversary of his April 21 death approaches.

State and federal authorities have spent the past year trying to identify the source of the fatal fentanyl dose, but no one has been arrested and it's unclear whether charges will ever be filed.

"We've gained a lot of progress over the last year," said Carver County chief deputy Jason Kamerud, "but there still is some more work to be done."

Kamerud gave no indication Monday of when the investigation might end, or its outcome.

The U.S. Drug Enforcement Administration turned over its findings to the U.S. attorney's office earlier this year without determining how Prince acquired the synthetic opioid that killed him, a source familiar with the case said. The U.S. attorney's office has declined to comment on the investigation.

The Carver County search warrant affidavits unsealed Monday showed that investigators searched Paisley Park within hours of Prince's death. Authorities found dozens of prescription medications that were not in typical prescription bottles, but rather were stored in various containers — such as vitamin bottles — scattered about the complex, including Prince's bedroom.

Authorities also discovered pharmaceutical bottles labeled in the name of Kirk Johnson, Prince's drummer, longtime friend and business associate, and a pamphlet on how to be weaned from drugs. But investigators found no prescriptions in Prince's name.

Prince, 57, died from an accidental, self-administered overdose of fentanyl, according to a report released last June by the Midwest Medical Examiner's Office. The report gave no indication of how he got the painkiller, nor did it list any other cause of death or "significant conditions." Authorities have said neither foul play nor suicide is suspected.

The Star Tribune reported in August 2016 that some of the dozens of prescription pills found at Paisley Park later tested positive for synthetic fentanyl and that investigators were working off the theory that Prince did not know the pills he ingested contained the narcotic.

A source with knowledge of the investigation said the autopsy found so much fentanyl in Prince's system that it would have been fatal for anyone.

Struggled with drugs

The documents unsealed Monday detail the music icon's final days and the challenge facing investigators.

Carver County authorities executed 11 search warrants between April 21, the day two of Prince's associates found his body, and September 19. Federal search warrants in the case are expected to remain under seal for several more months.

According to the warrant affidavits:

Witnesses at Prince's death scene told investigators that the musician had been struggling with opioid abuse and withdrawal. Johnson, who was also the head of Paisley Park security, told authorities that Prince reported "not feeling well" in the hours before he died. But Johnson, despite being close to the singer since the 1980s, told investigators that he didn't know that Prince was addicted to pain medication.

Johnson and Meron Bekure, Prince's personal assistant, found Prince unconscious in an elevator shortly after 9:30 a.m. April 21 and began screaming. Authorities were called to the complex in Chanhassen at 9:43 a.m., but attempts by emergency responders to revive him failed.

Prince had not been seen or heard from since 8 p.m. April 20.

Investigators found six people at the death scene, including Andrew Kornfeld, who had arrived in the Twin Cities at 6 a.m. that day to meet with Prince and assess him for a drug dependency program run by his father, Dr. Howard Kornfeld. He told detectives that he had controlled substances in his backpack that he brought to help Prince, but would not have administered them without a doctor present. He said his father didn't know that he had brought the medications.

Authorities found a pamphlet for Howard Kornfeld's "Recovery Without Walls" program in Paisley Park's Purple Rain room.

It's unclear whether authorities are pursuing a case against Andrew Kornfeld. But William Mauzy, a prominent Minneapolis attorney representing him, said Monday that Andrew Kornfeld is protected from criminal charges by a Minnesota law that generally shields anyone seeking medical assistance for a person overdosing on opioids.

Mauzy said Kornfeld declined to comment Monday because of patient confidentiality.

It's also uncertain whether investigators are examining the actions of Dr. Michael Todd Schulenberg, who, according to the warrant affidavits, told detectives that he had treated Prince twice — April 7 and 20 of last year, and had issued a prescription for oxycodone, an opiate, under Johnson's name to protect the star's privacy.

But Amy Conners, Schulenberg's attorney, said Monday that the doctor "never directly prescribed opioids to Prince, nor did he ever prescribe opioids to any other person with the intent that they would be given to Prince."

Scare in Moline

While the records Monday provided scant new details about the investigation, they did show that Prince, an intensely private person, traveled under the name Peter Bravestrong to help conceal his identity.

That name was on a luggage tag during his trip to Atlanta to perform in concert the week before his death.

It was on the return trip to the Twin Cities that Prince's private plane made an emergency stop in Moline, Ill., after the musician fell ill and passed out.

Paramedics scrambled to revive Prince on the tarmac, and he recovered after two shots of naloxone, an overdose antidote increasingly being used and often referred to by its brand name Narcan.

The affidavits said Johnson told doctors in Moline that Prince may have taken Percocet.

Prince was documented as suffering from an opiate overdose, but the musician refused treatment at the hospital.

Later, at a meeting with medical professionals "to assess and address" health concerns, Prince admitted to taking one or two "pain pills" that night.

The affidavits also showed that investigators have conducted interviews far and wide, and have pored over cellphone records and e-mail accounts.

Prince didn't use a cellphone because he'd been hacked years earlier, and communicated by e-mail and by landline.

Authorities also searched the cellphone records of several associates, including Johnson, whose name was on the labels of drug bottles found at Paisley Park. In addition to managing Paisley Park in recent years, Johnson coordinated tour logistics, organized concerts and after-parties, and contacted Schulenberg to help Prince with his hip pain.

Johnson did not did not respond to a phone call Monday seeking comment. However, F. Clayton Tyler, his attorney, issued a statement: "After reviewing the search warrants and affidavits released today, we believe that it is clear that Kirk Johnson did not secure nor supply the drugs which caused Prince's death."

Records show investigators also interviewed singer Judith Hill on June 16, and later learned that she had been involved romantically with Prince since fall of 2014.

Hill said she communicated with Prince through an e-mail account set up under the name of one of Prince's former managers.

Monday's disclosures come as Prince's relatives battle in Carver County District Court over his massive estate, which is estimated at $100 million to $300 million before taxes. Prince died without a will, and in the months since, dozens of people have come forward to make claims.

The list of heirs has yet to be finalized, but the judge handling the case has indicated that Prince's sister and five half-siblings will likely inherit his fortune.

Staff writers Pam Louwagie, Emma Nelson, Dan Browning and Jon Bream contributed to this report.

stephen.montemayor@startribune.com • 612-673-1755

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