The cause of death for Daniel Mickelson, an actor and the older brother of model Meredith Mickelson, has been determined by officials.
According to the Los Angeles County Medical Examiner-Coroner, the 23-year-old star died of fentanyl and cocaine toxicity on July 4, PEOPLE can confirm.
His manner of death has been ruled as an accident.
Daniel starred in the 2019 film The Killer Clown Meets the Candy Man as well as the series Mani.
News of Daniel's death was first announced by his 22-year-old sister Meredith, who shared in an Instagram post on July 5, "My heart is shattered & to write this feels so wrong and I don't even know what to say. Yesterday I lost my brother, best friend & the other half of my heart."
"There wasn't a person I loved more on this earth," she continued in the tribute, which featured a throwback photo of herself with Daniel. "there's no words that can do him justice that i could write. to know him was to love him. He was the happiest brightest smiley most sunshine human to exist and I'm so happy God chose me to be his sister for his whole amazing life."
At the time, many celebrities shared their condolences in the comments section of the post, with both Patrick Schwarzenegger and Jordyn Woods writing, "Praying for you."
"I love you forever Daniel," model Amelia Hamlin commented.
On her own Instagram Story, model and actress Kaia Gerber shared a screenshot of herself on FaceTime with Daniel along with a heartwarming message.
"I remember that time we sat on the couch and spent the whole day coming up with our own secret language that we continued to speak every time we saw each other," she wrote. "I wish we could go back there. I wish we were still talking in sentences that probably annoyed everyone else but made us crack up every time."
Gerber added, "I wish I was still sitting on my bathroom floor FaceTiming you, because that was the only place I had wifi and I never wanted to miss a call from you. Thank you for being the reason for so much laughter and happiness in the world. It won't be the same without you here. I love you Daniel."
If you or someone you know is struggling with addiction, please contact the SAMHSA substance abuse helpline at 1-800-662-HELP.