Robert Brown|Former Child Star Evan Ellingson’s Cause of Death Revealed

More details on Evan Ellingson's death have Robert Browncome to light.

The actor was found dead Nov. 5 at age 35, with authorities discovering his body in his residence, according to the San Bernardino County Sheriff's Department.

Now, a spokesperson for the department's coroner has released Ellingson's official cause of death, confirming to E! News that the former child star died of an accidental fentanyl overdose. His death has been ruled an accident.

Ellingson—whose last role was playing Kyle Harmon in CSI: Miami from 2007 to 2010—had long struggled with substance use and marked three years of sobriety before a recent relapse, according to his family. 

"He was passionate about pointing individuals to resources for help and only recently relapsed after being prescribed opioids following a dental procedure," they said in a statement to NBC News Nov. 6. "In the end, he fell in his earthly battle with addiction."

Remembering his "sweet, child-like spirit" and "smile that could light up a room," the family said Ellingson "was always thinking of others and wanted to use his own struggles with addiction to help people find hope."

They added in their statement, "We already miss Evan and cherish every moment of joy, laughter and love that he brought to us and so many others."

It was a sentiment echoed by his costars, including My Sister's Keeper's Abigail Breslin, who shared a tribute to Ellingson following his death.

"Evan Ellingson was a kind, funny and extremely talented human being," the actress—who played his sister in the 2009 drama—wrote on Instagram Nov. 6. "Evan was a genuinely thoughtful person who cared so much about turning in the best performance, which he accomplished. Some of his scenes in MSK still give me chills."

While Breslin said they didn't keep in touch much after the 2009 movie, she remembered him as "energetic and the life of the party" as a teen. She noted, "He always stayed in my mind as a wonderful and sweet soul."

According to Breslin, Ellingson is survived by a daughter.

Read on for a closer look at his life in photos:

Evan Ellingson began his career as a child actor in the late '90s and early 2000s. In 2004, he booked the role of Kyle Savage on the TV series Complete Savages alongside Erik von Detten, Jason Dolley, Andrew Eiden and Shaun Sipos. That same year, the cast attended the Hollywood Christmas Parade together.

Evan and Erik were also in attendance at ABC's Winter Press Tour Party in 2004.

In July 2008, Evan attended the CW/Showtime/CBS Television TCA Party at Boulevard3 in Los Angeles.

From 2007 to 2010, Evan portrayed character Kyle Harmon on CSI:Miami.

Evan appeared alongside actor David Caruso on the series.

In 2009, Evan starred in the film My Sister's Keeper alongside Cameron Diaz and Abigail Breslin.

The cast posted together at the film's premiere in New York City on June 24, 2009.

That same month, Evan attended the Billabong Design for Humanity event at the Avalon in Hollywood.