Franco Columbu, a bodybuilder, boxer and actor who appeared in the films The Terminator and Conan the Barbarian alongside his close friend Arnold Schwarzenegger, has died. Columbu was 78.

The Italian star passed away Friday after drowning in his native Sardinia, The Associated Press reported.

He lived in Los Angeles, but had been vacationing in Sardinia when he fell ill while swimming. He was pronounced dead at a hospital in the city of Olbia.

Columbu was a former Mr. Olympia and Mr. Universe. Schwarzenegger described him as his “best friend” in an online tribute.

“I love you Franco,” Schwarzenegger tweeted Friday. “I will always remember the joy you brought to my life, the advices you gave me, and the twinkle in your eye that never disappeared.”

The Hollywood legend and former California governor also shared a link to an essay he wrote on Medium about Columbu.

“From the minute we met in Munich, you were my partner in crime,” Schwarzenegger wrote. “We pushed each other, we competed with each other, and we laughed at every moment along the way.”

“When I finally got to America, I was alone. I’d left my family, my country, my whole life behind,” he continued. “So when I asked Joe Weider to bring you to train with me, it was because I knew I wasn’t the same without my best friend. I could thrive without money, without my parents, but I couldn’t thrive without you.”

He went on to say the two had been friends for 54 years.

“I am devastated today. But I am also so, so grateful for the 54 years of friendship and joy we shared,” he added. “The pumps, the chess games, the construction work, the meals, the pranks, the life lessons — we did it all together. We grew and we learned and we loved. My life was more fun, more colorful, and more complete because of you.”