Daniel Mickelson's cause of death has been determined nearly three months after he died at the age of 23.
The rising Hollywood star, who was the older brother of model Meredith Mickelson, passed away due to fentanyl and cocaine toxicity on July 4, the Los Angeles County Medical Examiner-Coroner confirmed to E! News.
The actor's manner of death was ruled an accident by officials.
Over the Fourth of July weekend, Meredith broke the news on Instagram about her brother's passing and remembered his life with a touching tribute.
"my heart is shattered & to write this feels so wrong and i don't even know what to say," the 22-year-old model began her caption on July 5, alongside a throwback photo of themselves as kids. "Yesterday i lost my brother, best friend & the other half of my heart."
She continued, "There wasn't a person i loved more on this earth. theres no words that can do him justice that i could write."
Meredith concluded her post, "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."
Following the model's moving message, many fellow stars expressed their heartache over Daniel's loss, including Jordyn Woods, Patrick Schwarzenegger and others.
"Praying for you," Jordyn commented, with Amelia Hamlin responding, "i love you forever daniel."
Kaia Gerber honored Daniel on Instagram Stories, writing at the time, "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. I wish we could go back there."
"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," she added. "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."
The Hollywood newcomer—who appeared in The Killer Clown Meets the Candy Man film and Mani TV series—was also remembered by his girlfriend, Maddie Haley.
"You lit up every room with your contagious smile and never failed to make anyone happy," she wrote in part on July 5. "There wasn't one day that went by where you didn't go out of your way to make me feel special and loved."
She added, "I'm not sure how I'm going to get through this but I'm going to be strong for you because I know it's what you would have wanted. Everything I do now is for you."