Exactly six weeks after his April 21 death, the world now knows what killed Prince Rogers Nelson. The Star Tribute reports that the 57-year-old uber-musician died from an accidental overdose of fentanyl.

The Midwest Medical Examiner’s Office released its autopsy report on Prince today (June 2). It does not list any other cause of death or “significant” health conditions, and says that the 112-pound singer self-administered the drug. It has been widely reported that the Minneapolis star was scheduled to meet with a doctor who specialized in opioid addiction just a week after he was discovered in an elevator in his home.

Fentanyl is a prescription narcotic pain killer that the National Institutes of Health and National Institute on Drug Abuse say should be used to treat patients with severe pain, particularly adults who experience sudden pain episodes while undergoing long-term cancer treatment and those who need to manage pain following surgery. Breathing difficulties are listed among its many potential side effects. It is the strongest opioid available—upwards of 50 times more potent than morphine.

In March 2015, the U.S. Drug Enforcement Administration (DEA) issued an alert warning of a spike in fentanyl-related deaths. “Drug incidents and overdoses related to fentanyl are occurring at an alarming rate throughout the United States and represent a significant threat to public health and safety,” DEA Administrator Michele M. Leonhart said.

According to the Star Tribune, Prince was treated by a local doctor for withdrawal symptoms associated with opioid addiction the day before he died, including fatigue and anemia. The Carver County Sheriff’s Office is still investigating his death, with an eye toward determining where he obtained prescriptions for the fentanyl.

Read the publicly released portion of the report here.