Euphoria star Angus Cloud died of "acute intoxication following an accidental overdose", a coroner told People magazine in the US.
The actor who played Fez O'Neill had cocaine, methamphetamine, fentanyl and benzodiazepines in his system at the time of his death, according to the Alameda County Coroner.
In a statement at the time of his death on August 1, his family said he had been struggling with the news of father's recent death.
"It is with the heaviest heart that we had to say goodbye to an incredible human today," their statement read.
"As an artist, a friend, a brother and a son, Angus was special to all of us in so many ways.
"The only comfort we have is knowing Angus is now reunited with his dad, who was his best friend.
"Angus was open about his battle with mental health and we hope that his passing can be a reminder to others that they are not alone and should not fight this on their own in silence. We hope the world remembers him for his humour, laughter and love for everyone."
Euphoria star Zendaya also paid tribute after his death.
Posting to Instagram, she said she was "so grateful" to have known the actor, who played the big-hearted drug dealer Fezco 'Fez' O'Neill in the hit HBO series.
"Words are not enough to describe the infinite beauty that is Angus (Conor). I'm so grateful I got the chance to know him in this life, to call him a brother, to see his warm kind eyes and bright smile, or hear his infectious cackle of a laugh (I'm smiling now just thinking of it)," she wrote, alongside a black and white photo of a smiling Cloud.
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