Al Pacino is paying tribute to Diane Keaton, his former costar and past romantic partner.

Keaton died of pneumonia at age 79 on Saturday, Oct. 11, and Pacino, who has been processing the news while filming a movie in Paris, spoke out in a message shared with Deadline on Thursday, Oct. 16.

“When I first heard the news, I was shaken,” said Pacino, 85. “Diane was my partner, my friend, someone who brought me happiness and on more than one occasion influenced the direction of my life. Though over 30 years has past since we were together, the memories remain vivid, and with her passing, they have returned with a force that is both painful and moving.”

The actors, who shared the screen in the Godfather films as Michael Corleone and Kay Corleone, struck up a romantic relationship off camera. Keaton, who never married, also dated Woody Allen and Warren Beatty during her life.

Diane Keaton; Al Pacino.Matt Winkelmeyer/Getty; Allen Berezovsky/Getty

“She lived without limits, and everything she touched carried her unmistakable energy,” Pacino continued. “She opened doors for others, inspired generations and embodied a once-in-a-lifetime gift that radiated through her work and her life.”

The actor added, “People will miss her, but more than that, they will remember her. She left a mark that cannot fade. She was unstoppable, resilient and above all, deeply human. I will always remember her. She could fly — and in my heart, she always will.”

Al Pacino and Diane Keaton in “The Godfather”.Paramount Pictures/Getty

In 2017, Keaton told PEOPLE she “had a crush” on Pacino when they worked together on The Godfather in 1971, and when they became a couple, “I was mad for him. Charming, hilarious, a nonstop talker,” she recalled at the time. “There was an aspect of him that was like a lost orphan, like this kind of crazy idiot savant. And oh, gorgeous!”

Keaton said she eventually gave Pacino an ultimatum when he wouldn’t commit to marrying her, and then it was over: “I worked hard on that one. I went about it in not a perfect way.”

The Godfather director Francis Ford Coppola also honored Keaton’s memory, writing on Instagram Oct. 12, “Words can’t express the wonder and talent of Diane Keaton. Endlessly intelligent, so beautiful.”

“I saw her in the film ‘Lovers and Other Strangers’ and knew I had to have her play Kay in The Godfather, (which she told me she based on my wife Ellie) and her wonderful work in ‘Annie Hall’ while simultaneously setting a new fashion trend. Everything about Diane was creativity personified,” added Coppola, 86.

Keaton is survived by her two kids, daughter Dexter, 29, and son Duke, 25.