Ryan O'Neal died after a long battle with heart disease.
According to a death certificate shared by The Blast on Dec. 23, the Love Story actor's passing on Dec. 8 was caused by congestive heart failure. The document also shows that for years prior to his death at 82, Ryan suffered from cardiomyopathy, which can lead to heart failure, as it reduces the ability of the heart muscle to pump blood.
E! News has reached out to the actor's rep for comment and has not heard back.
Patrick O'Neal, one of the star's four children, had announced the star's death the day he died. "This is the toughest thing I've ever had to say," the 56-year-old wrote on Instagram. "My dad passed away peacefully today, with his loving team by his side supporting him and loving him as he would us."
He added, "My father Ryan O'Neal has always been my hero. I looked up to him and he was always bigger than life."
Born in 1941, Ryan rose to fame playing Rodney Harrington on ABC's Peyton Place in the '60s. His breakout big screen role came in 1970, when he played preppy Harvard law student Oliver opposite Ali McGraw in the film Love Story.
Ryan went on to star in movies such as Paper Moon, Barry Lyndon and What's Up, Doc?. His most recent onscreen acting role was that of Max Keenan, a recurring character on the TV show Bones, which he played between 2006 and 2017.
In addition to Patrick, who he shared with ex-wife Leigh Taylor-Young, Ryan is also survived by daughter Tatum O'Neal, 60, and son Griffin O'Neal, 59—his kids with first ex-wife Joanna Moore, and Redmond O'Neal, 38—his son with late actress Farrah Fawcett.
Tatum, who at age 10 became the youngest Oscar winner for her performance alongside her father in Paper Moon, also paid tribute to the late actor on her Instagram.
"Thank you everyone for all your love and support," she said in a Dec. 10 Instagram video. "He is in Heaven now."