The 26-year-old hip-hop artist, whose real name was Malcolm James McCormick, "died from mixed drug toxicity (fentanyl, cocaine and ethanol)," according to a statement from the Los Angeles County coroner's office.
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The manner of death was ruled accidental.
McCormick was found unresponsive Sept. 7 at his home in the 11600 block of Valleycrest Drive. He was pronounced dead at the scene by emergency responders.
The Pittsburgh native was in a two-year relationship with Ariana Grande that ended earlier this year.
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His music, which often examined his depression and drug use, won him fans among some of the biggest names in hip-hop.
Performers at a tribute concert for him last week included Chance the Rapper, Travis Scott and John Mayer.
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The Associated Press contributed to this report.