Diane Keaton Died Within Days After Bacterial Pneumonia Infection: 'She Declined Very Suddenly'

Diane Keaton's health declined rapidly in the final days before her sad death.

New details surrounding the Annie Hall actress' quick decline have been exposed following the reveal of Keaton's official cause of death — primary bacterial pneumonia.

According to her death certificate, Keaton died within days after contracting the lung infection.

The document confirmed primary bacterial pneumonia as Keaton's immediate cause of death and revealed she had it days before her passing.

No other significant contributing factors were listed on the certificate, though it noted Keaton will be cremated.

Sources previously spoke out about the status of Keaton's health in the weeks before her death.

"She declined very suddenly, which was heartbreaking for everyone who loved her. It was so unexpected, especially for someone with such strength and spirit," a pal told People. "Even longtime friends weren’t fully aware of what was happening."

Keaton's family "chose to keep things very private," the insider noted.

Oscar-winning songwriter Carole Bayer Sager revealed Keaton looked "very thin" when she "saw her two or three weeks" before her death.

"She had lost so much weight," Sager confessed to the news outlet, admitting she was "stunned" by Keaton's drastic body changes — which she first noticed after spending time apart from the Father of the Bride star due to the California wildfires that caused several celebrities to be displaced from their homes back in January.

Keaton's family addressed the Hollywood legend's cause of death in a statement to People on Wednesday, October 15.

"The Keaton family are very grateful for the extraordinary messages of love and support they have received these past few days on behalf of their beloved Diane, who passed away from pneumonia on October 11," her loved ones expressed.

The message continued, "She loved her animals and she was steadfast in her support of the unhoused community, so any donations in her memory to a local food bank or an animal shelter would be a wonderful and much appreciated tribute to her."

While Keaton never married, she's survived by her two children — a daughter, Dexter, and a son, Duke, whom she adopted in 1996 and 2001, respectively.

The late mom-of-two became a parent for the first time when she adopted Dexter a few months after she was born on December 15, 1995.

Meanwhile, Duke joined their family roughly one year after he was born on February 8, 2000.

Diane reflected on motherhood two decades before her sad death during an interview with Life Magazine.

"The shocking thing is that I worry differently now. Before kids, if I worried, it was only about myself, but that's all you do is worry as a parent. It's rule number one in parenting: secretly worry without letting the kids know you're worried," she explained.