A doctor who saw Prince in the days before he died had prescribed the painkiller oxycodone under the name of Prince’s friend to protect the musician’s privacy, according to court documents unsealed Monday that revealed nothing about how the pop superstar got the fentanyl that actually killed him.

The affidavits and search warrants were unsealed in Carver County District Court in Minnesota as the yearlong investigation into Prince’s death continues. The documents show authorities searched the musician’s estate at Paisley Park, cellphone records of Prince’s associates and Prince’s email accounts to try to determine how he got the fentanyl, a synthetic drug 50 times more powerful than heroin.

Oxycodone, the generic name for the active ingredient in OxyContin, was not listed as a cause of Prince’s death, but it is part of a family of painkillers driving the nation’s overdose and addiction epidemic, according to the U.S. Centers for Disease Control and Prevention.

Prince was 57 when he was found alone and unresponsive in an elevator at his Paisley Park home on April 21.

One affidavit says Dr. Michael Todd Schulenberg, a family doctor who saw Prince April 7, 2016, and again on April 20, acknowledged to authorities that he prescribed oxycodone for Prince the same day as an emergency plane landing a few days earlier, “but put the prescription in Kirk Johnson’s name for Prince’s privacy.”

— Associated Press