When the autopsy report for Prince surfaced in June, it became clear that the singer died from a lethal dose of a powerful opioid called fentanyl.
Now investigators have found reason to believe that he did not know what he was taking.
During a search of Prince's Minnesota estate after his death in April, authorities found an Aleve bottle filled with two dozen pills.
The pills tested positive for fentanyl, a drug that can be up to 100 times as powerful as morphine.
But they were marked "Watson 385".
That's a label found on a generic painkiller that contains acetaminophen and hydrocodone - the ingredients of many commonly prescribed painkillers, including Vicodin.
So, on the surface, the pills looked to be standard painkillers for moderate to severe pain. In reality, they contained a drug so powerful that the Centers for Disease Control and Prevention calls it a "threat to public health and safety".
While it's still unclear whether those particular pills caused Prince's death, the Minneapolis Star Tribune reported that the discovery is prompting investigators to lean toward the theory that Prince did not know that the pills he took contained fentanyl.
He might have been a casualty of a counterfeit pill scheme that authorities say is sweeping the nation and exacerbating the opioid-addiction crisis.
Fentanyl, when properly prescribed by a doctor, is a drug approved for managing severe chronic pain.
As the use of heroin has boomed, so, too, has illegal manufacturing of fentanyl, which is 25 to 50 times as strong. This illegal fentanyl is often mixed with other drugs, then sold in highly potent forms, such as pills.
Authorities believe the illegally manufactured fentanyl is being produced in China, then sold to drug traffickers in the United States, Canada and Mexico. A kilogram of fentanyl powder costs only a few thousand dollars.
Using pill presses they can turn that 1kg of fentanyl into more than 600,000 pills, bringing profits of millions for the traffickers. They sell the pills to people looking for painkillers, who often have no idea what they're about to take.
As investigators work to find out how the fentanyl-laced pills came to be in Prince's possession, the DEA is warning: Overdoses and deaths from counterfeit drugs containing fentanyl are only going to increase.