Story highlights
- Law enforcement sources tell CNN that investigators looking at a doctor's relationship with Prince, his team
- Attorney for Dr. Michael Schulenberg says he is cooperating
- The Minnesota doctor says he saw Prince twice
(CNN)The focal point of the investigation into Prince's death appeared to be shifting Wednesday to the role of a Minnesota doctor revealed in a search warrant to have seen the entertainer twice in the weeks before he died.
The search warrant, obtained by the Los Angeles Times and the Minneapolis Star Tribune, also reveals Dr. Michael Schulenberg went to Prince's Paisley Park studios on April 21, the day the musician died, apparently to deliver test results.
Investigators are interested in learning more about the relationship between Schulenberg and Prince, as well as members of the musician's inner circle, law enforcement officials told CNN on Wednesday.
Authorities said they have not found a valid prescription for opioid medication, either on Prince's person or at Paisley Park. The evidence found so far doesn't suggest that Prince was "doctor shopping" -- or seeking prescriptions from multiple doctors -- as has happened in other prominent celebrity deaths, law enforcement officials said previously.
Instead, investigators are focused on the possibility that so-called "drug runners" were obtaining the medications for Prince.
It's unclear whether the singer was being treated for any health issues. Results of the autopsy are pending.
Office search
The search warrant documents published by the newspapers show investigators sought medical records from the clinic where Schulenberg worked until Tuesday, but do not describe why the doctor was treating Prince.
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In a search warrant affidavit, Carver County Sheriff's Office Detective Chris Nelson said Schulenberg had told him he had seen Prince on April 7 and again the day before his death.
He also had issued the singer a prescription to be filled at a Walgreen's store. The affidavit does not disclose what the prescription was for, however.
Amy Conners, an attorney for the doctor, told CNN: "Dr. Schulenberg is cooperating with investigators."
Schulenberg has not been accused of any wrongdoing.
Investigators have been looking into the cause of the 57-year-old artist's death. Results of an April 22 autopsy and toxicology tests are pending.
The search warrant documents obtained by the Times and Star Tribune are no longer publicly available. The documents are under seal and should not have been released, said Nancy Peters of the Hennepin County District Court.
Photos: Prince: The artist
Singer and songwriter Prince performs onstage during his Purple Rain Tour in 1984. The artist, who pioneered "the Minneapolis sound" and took on the music industry in his fight for creative freedom, died in April 2016 at age 57.
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Photos: Prince: The artist
Prince performs in New York in 1980. Prince won seven Grammy Awards, and earned 30 nominations. Five of his singles topped the charts and 14 other songs hit the Top 10.
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He performs at the Palladium in New York in 1981.
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Prince at the Lyceum in London in 1981.
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Prince and Apollonia Kotero in a scene from the movie "Purple Rain," which was released in 1984.
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Prince, seen here on set, won an Oscar for the original song score for the classic film.
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Photos: Prince: The artist
Prince performs in New York in 1984. Controversy followed the singer and that, in part, made his fans adore him more. His 1984 song, "Darling Nikki," details a one-night stand and prompted the formation of the Parents Music Resource Center. Led by Al Gore's then-wife, Tipper Gore, the group encouraged record companies to place advisory labels on albums with explicit lyrics.
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Photos: Prince: The artist
Prince performs at the Joe Louis Arena in Detroit in 1984.
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Prince performs live at the Fabulous Forum in 1985, in Inglewood, California.
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Prince in 1985.
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Prince, circa 1985.
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Prince performs live at the 1985 Fabulous Forum in Inglewood, California. He created what became known as the Minneapolis sound, which was a funky blend of pop, synth and new wave.
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Prince in the United Kingdom in the 1980s.
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Prince, circa 1985.
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Prince in a scene from the 1986 film "Under the Cherry Moon."
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Prince performs in London in 1986.
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Prince performs in London in 1986.
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Prince performs at London's Wembley Arena in 1986.
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Prince in 1987.
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Prince performs at Wembley Arena in London in 1988.
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Photos: Prince: The artist
The singer's predilection for lavishly kinky story-songs earned him the nickname "His Royal Badness." He is also known as the "Purple One" because of his colorful fashions. He is seen here in 1990.
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Prince performs in 1990.
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Prince, 1990.
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Prince performs during "The Nude Tour" in Birmingham, United Kingdom, in 1990.
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Prince listens to the crowd during a 1991 concert.
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Prince performs at the MTV Video Music Awards in Los Angeles in 1991.
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Prince performs at the Globe Arena in Stockholm in 1993.
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Prince arrives at the Ritz Hotel in Paris in 1994.
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A disguised Prince appears at a Virgin Records in London in 1995.
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Photos: Prince: The artist
As dozens of singers perform "We Are The World" on the 10th anniversary of the African famine relief anthem, the artist formerly known as Prince stands sucking on a lollipop next to Quincy Jones at the American Music Awards in Los Angeles in 1995.
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Prince poses for a photo in Toronto in 1996.
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Photos: Prince: The artist
Muhammad Ali pats Prince's head prior to a news conference where they were to announce plans for a benefit concert in 1997.
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Prince performs in 1998.
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A disguised Prince speaks at GQ magazine's third annual Men of the Year Awards in 1998.
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Prince, circa 1999.
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Photos: Prince: The artist
Prince performs in Hong Kong on October 17, 2003. Prince's concert was the the opening act in a four-week government-sponsored music festival titled "Hong Kong Harbor Fest," aimed at boosting the image of SARS-battered Hong Kong.
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Photos: Prince: The artist
Prince arrives with his then-wife, Manuela Testolini, for the 77th Academy Awards on February 27, 2005, in Los Angeles.
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Prince at the 2005 NAACP Image Awards in Los Angeles.
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Prince performs during a news conference for Super Bowl XLI in 2007.
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Photos: Prince: The artist
He left his imprint on many aspects of popular culture, from film to movies to sports to politics. As the Minnesota Vikings prepped to take on the New Orleans Saints in the 2010 NFC championship game, Prince wrote a fight song entitled "Purple and Gold" to inspire his home team. The Vikings lost. He was the half-time performer at the Super Bowl in 2007 in Miami Gardens, Florida, seen here.
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Photos: Prince: The artist
Prince performs onstage during the 2007 NCLR ALMA Awards.
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Prince performs on the runway at the spring/summer 2008 collection fashion show by Matthew Williamson during London Fashion Week in September 2007.
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Prince performs during his Welcome 2 America tour at Madison Square Garden in 2011 in New York.
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Photos: Prince: The artist
American pop legend Prince is pictured performing on the final night of the Hop Farm Music Festival in Kent, United Kingdom, in 2011.
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Prince performing at the Femoren on August 6, 2011, in Copenhagen, Denmark.
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Prince on stage with singer Mary J. Blige during the 2012 iHeartRadio Music Festival in Las Vegas.
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Prince presents the winner for Record of the Year to Gotye and Kimbra during the 55th Grammy Awards in 2013.
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A year later, Prince performs during the 2013 Billboard Music Awards in Las Vegas.
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Prince performs at the 2013 Skanderborg Festival in Denmark.
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Prince is seen in the stands during the 2014 French Open in Paris.
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Left to right: Zooey Deschanel, Prince, and Jake Johnson in a scene from the TV show "New Girl" which aired in 2014.
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Photos: Prince: The artist
Prince speaks at the 2015 Grammy Awards in Los Angeles. Additionally, last year, Prince released the song "Baltimore," addressing the unrest after the death of Freddie Gray while in police custody. He performed at a benefit concert in the city and gave a portion of the proceeds to youth groups in Baltimore.
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Photos: Prince: The artist
Prince tweeted his passport photo on February 11. The photo quickly took the Internet by storm.
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Attorney: Siblings spoke of Percocet addiction
Last week, the former attorney for two of Prince's dead siblings says they had revealed Prince had an addiction to Percocet decades ago.
Prince's half-brother, Duane Nelson, said he used to get the drug for Prince to help him come down after shows, attorney Michael B. Padden said. Nelson died in 2013.
Another half-sibling, Lorna Nelson, also alleged drug use by Prince, but was not involved in getting drugs for him, Padden said. She died in 2006.
Schulenberg: What we know
Drug expert sent to Prince on 'life-saving mission' 01:39
According to records with the Minnesota Board of Medical Practice, Schulenberg is certified in family medicine and has no criminal convictions.
He is a 1995 graduate of the Oregon Health Sciences University in Portland, Oregon, according to the records.
The clinic where Schulenberg practiced family medicine said he was no longer working there as of Tuesday. Deborah Cannon with North Memorial Clinic gave no details as to why Schulenberg was no longer employed.
CNN called several numbers listed for the doctor and left a request for comment on his voice mail. Calls and emails by CNN to his attorney were not immediately returned.
"Revisiting the scene"
The revelations accompanied fresh activity at the Paisley Park complex where Prince died.
Agents from the U.S. Drug Enforcement Administration and local sheriff's deputies were at Prince's home on Tuesday as part of an ongoing investigation into the music legend's death, a law enforcement official told CNN.
The DEA agents were executing a federal search warrant, the source said. They were looking for additional evidence that could help explain the source of prescription opioids, sources told CNN.
CNN affiliate WCCO reported more than a dozen vehicles were at Paisley Park.
The Carver County Sheriff's Office tweeted Tuesday that detectives were "revisiting the scene" as part of their "complete investigation."
The U.S. Attorney's Office and the DEA announced last week they were joining forces with local investigators, led by the sheriff's office in Carver County, to investigate Prince's death.
The county includes the Minneapolis suburb of Chanhassen, where Prince's Paisley Park complex is located.
Source: Opioids found at scene
Officials have yet to publicly comment on what killed Prince. But attention has increasingly focused on the possible involvement of opioid pain killers.
The day before Prince died, his team called an eminent opioid addiction specialist in California seeking urgent help for the singer, William Mauzy, an attorney working for the specialist and his son, said last week.
The specialist, Dr. Howard Kornfeld, couldn't get there immediately so he sent his son, Andrew Kornfeld, on an overnight flight to Minnesota. The goal was for the younger Kornfeld to help evaluate Prince's health and encourage him to enter treatment for pain management and potential addiction issues, Mauzy said.
Why are opioids so addictive? 01:09
Andrew Kornfeld called 911 after representatives of the singer discovered him unresponsive in an elevator the morning of April 21, Mauzy said.
Opioids reduce pain by switching off pain receptors in the brain.
They are among the most widely prescribed drugs in the United States, the Centers for Disease Control and Prevention says. Prescription opioids include painkillers such as morphine, oxycodone and hydrocodone, according to the CDC.
Opioids produce an increased pain tolerance and a sense of euphoria. They trigger a craving when the drug is absent.
