Prolific voice actor Peter Cullen, who provided the deep and resonant voice of Optimus Prime in the “Transformers” films and 1980s animated series, has died at 85.

Cullen’s representative Kevin Motely said he died Wednesday at his home in Los Angeles. Details about a cause of death were not immediately available.

In a statement, Cullen’s family referenced a quote that Cullen often shared when he spoke at fan events.

“Peter Cullen passed away peacefully, surrounded by his loving family and held in the hearts of his many friends and countless fans worldwide,” the family said. “His family asks that you honor his remarkable legacy by serving your communities and leading others with compassion, integrity, and loyalty and always remember, ‘Be strong enough to be gentle.'”

Cullen frequently referenced the quote when speaking to audiences and cited it as part of the inspiration behind the sonorous voice of the leader of the Autobots. It was a piece of advice he said was shared by his brother Larry, a captain in the Marine Corps, before he auditioned for the role of a “hero truck” in the 1980s.

“I’m going to an audition. I’m auditioning to be a truck,” Cullen told the audience at a 2023 TFcon fan event. “I said, ‘But Larry, he’s a hero truck.’ And, his face got somber and he said, ‘Peter, if you’re going to be a hero, be a real hero. Don’t be a Hollywood hero type with the yelling and screaming. Be strong enough to be gentle.’

“So, his voice is ringing in my ears as I drive to the audition.”

Before the audition, Cullen only knew he would be reading for the part of a truck.

“You’re always auditioning for something in animation that’s a little off of the norm,” Cullen told the AP in 2019.

Cullen voiced Optimus Prime in the animated series and returned to the role years later for the Michael Bay film series. He also provided the voice effects of the Predator, who took on Arnold Schwarzenegger in the 1987 film of the same name.

Born in Montreal, Canada, Cullen’s baritone voice led to a career in radio before he became the announcer on the “The Smothers Brothers Comedy Hour” in 1967.

Cullen earned a long list of credits during his prolific voice acting career that spanned more than five decades. His work included the voice behind the melancholy donkey Eeyore in the “Winne the Pooh” franchise and roles in several animated series.

Cullen provided the sound of King Kong’s roar in the 1976 film and was the robotic voice of the villainous KARR vehicle in the “Knight Rider” TV series.

The mid-1980s animated “Transformer” series was inspired by a popular line of toys that could transform from robots to cars and trucks. The series followed the battle between two opposing factions — the Autobots and Decepticons, led by Megatron.

Cullen’s voice became synonymous with the heroic Prime, and he reprised the role decades later for the live-action films, starting with “Transformers” in 2007. Cullen delivered some of the films’ most memorable lines, such as this phrase from the first movie: “I am Optimus Prime, and I send this message to any surviving Autobots taking refuge among the stars: We are here. We are waiting.”

Another well-known Cullen-voiced movie quote reads, “Fate rarely calls upon us at a moment of our choosing.”

Among Cullen’s many other TV credits are “Tom & Jerry,” “The Addams Family,” “My Little Pony,” “Chip ‘n’ Dale Rescue Rangers,” “The Flintstone Kids,” “Duck Tales,” “Rainbow Brite,” “Rambo,” “Ghostbusters,” “Pound Puppies” and “Teenage Mutant Ninja Turtles.”

Cullen was honored with a handprints ceremony in 2014 at TCL Chinese Theatre in the heart of Hollywood.