Evan Ellingson’s cause of death has been revealed less than a month after the actor died at age 35.

Ellingson died from an accidental overdose of fentanyl, the San Bernardino County Sheriff’s Department confirmed to The Hollywood Reporter on Tuesday.

On Nov. 5, the My Sister’s Keeper star was found dead at his Fontana, California, residence, the Sheriff’s Department said at the time. TMZ previously reported that Ellingson was staying at a sober living home when he died.

Though he hadn’t appeared onscreen in 10 years, Ellingson had several roles in projects throughout his childhood and teenage years. His most notable included playing Jesse Fitzgerald, the teen son of Cameron Diaz’s Sara, in 2009’s adaptation of Jodi Picoult’s My Sister’s Keeper. He starred opposite Abigail Breslin and Sofia Vassilieva in the film.

Ellingson, who reportedly started acting at age 10, also played Kyle Harmon, the son of David Caruso’s Lt.