This has been an incredibly sad week.

After saying goodbye to legends like Dolly Parton and Tim Curry, fans are now mourning another familiar voice — Peter Cullen, the man behind some of the most beloved characters of our childhood.

Cullen, the Canadian-born voice actor best known as Optimus Prime in Transformers and Eeyore in Winnie the Pooh, has died at 85.

Cullen’s agent confirmed that Cullen passed away Wednesday at his home in Los Angeles. His cause of death has not been revealed.

TMZ was the first outlet to break the heartbreaking news.

“Peter Cullen passed away peacefully, surrounded by his loving family — and held in the hearts of his many friends and countless fans worldwide,” his family said.

They asked fans to “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.’”

For millions of fans, Cullen’s deep, unmistakable voice was Optimus Prime. He first brought the heroic Autobot leader to life in the original animated Transformers series in the 1980s, beginning a role that would follow him for decades.

When Optimus Prime was killed in the 1986 animated movie, fans were devastated. The reaction was so intense that the character was eventually brought back, with Cullen later returning to the role for Michael Bay’s live-action Transformers films beginning in 2007.

But Optimus Prime was only part of Cullen’s extraordinary legacy.