Diane Keaton’s Health Declined ‘Suddenly’ in Past Few Months, Report Reveals

Prior to her death, Diane Keaton’s health had apparently been declining.

It was revealed on Saturday that the Oscar-winning actress had died at 79.

Although not much information has been revealed surrounding the circumstances of her death, a friend of Keaton’s tells PEOPLE that she “declined very suddenly, which was heartbreaking for everyone who loved her. It was so unexpected, especially for someone with such strength and spirit.”

“In her final months, she was surrounded only by her closest family, who chose to keep things very private,” the source continued. “Even longtime friends weren’t fully aware of what was happening.” What exactly those health problems were is unknown, but it seems like Keaton and her family wanted to keep things as private as possible, which is understandable.

Keaton’s death has sent shockwaves through Hollywood, as many fans and celebrities paid tribute to the legendary actress and her extensive filmography. In a statement via Deadline, her frequent co-star Robert De Niro said, “I am very sad to hear of Diane’s passing. I was very fond of her, and the news of her leaving us has taken me totally by surprise. I was not expecting her to leave us. She will be missed. May she rest in peace.”

“It’s hard to believe…or accept…that Diane has passed.” Keaton’s Book Club co-star Jane Fonda said on Instagram. “She was always a spark of life and light, constantly giggling at her own foibles, being limitlessly creative…in her acting, her wardrobe, her books, her friends, her homes, her library, her world view. Unique is what she was. And, though she didn’t know it or wouldn’t admit it, man she was a fine actress!”

Born Diane Hall in Los Angeles on Jan. 5, 1946, Keaton frequently collaborated with director Woody Allen, including for the movie Annie Hall in the titular role, for which she won the Oscar for Best Actress in 1977. Her breakout role was Kay Adams-Corleone in Francis Ford Coppola’s The Godfather in 1972 and its sequels in 1974 and 1990. Other notable credits include Reds, Marvin’s Room, Something’s Gotta Give, Baby Boom, Father of the Bride, The First Wives Club, The Family Stone, and Finding Dory, among others.

A source told PEOPLE that Keaton, who listed her “dream home” in March, was frequently seen walking her dog in her neighborhood. “She lived in Brentwood for many years,” they said. “She loved her neighborhood. Up until just a few months ago, she’d walk her dog every day. She was usually dressed the same, with a hat and her signature sunglasses, regardless of the weather. She was always very nice, funny, and chatty. She’d talk to her dog like he was a person. She was eccentric and had this old-school Hollywood aura. She was very, very special.”