Hollywood director and actor Rob Reiner and his wife Michele have been found dead at their Los Angeles home.
Investigators believe they suffered stab wounds and a family member is being questioned by investigators, an LAPD official said.
The Reiner family confirmed the deaths in a statement to Variety.
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"It is with profound sorrow that we announce the tragic passing of Michele and Rob Reiner," the family said.
"We are heartbroken by this sudden loss, and we ask for privacy during this unbelievably difficult time."
The Los Angeles Fire Department said it responded to a medical aid request shortly after 3.30pm (10.30am AEDT) and found a 78-year-old man and 68-year-old woman dead inside.
Reiner turned 78 in March.
Detectives with the Robbery Homicide Division were investigating an "apparent homicide" at Reiner's home, Captain Mike Bland with the Los Angeles Police Department said.
Los Angeles authorities have not confirmed the identities of the people found dead at the residence in the upmarket Brentwood neighbourhood on the city's west side that's home to many celebrities.
Reiner was long one of the most prolific directors in Hollywood, and his work included some of the most memorable movies of the 1980s and '90s, including This is Spinal Tap, A Few Good Men, When Harry Met Sally and The Princess Bride.
His role as Meathead in Norman Lear's 1970s TV classic All in the Family, alongside Carol O'Connor's Archie Bunker, catapulted him to fame and won him two Emmy Awards.
Relatives of Lear, the legendary producer who died in 2023, said they were bereft by the news.
"Norman often referred to Rob as a son, and their close relationship was extraordinary, to us and the world," said a Lear family statement.
"Norman would have wanted to remind us that Rob and Michele spent every breath trying to make this country a better place, and they pursued that through their art, their activism, their philanthropy, and their love for family and friends."
Messages to Reiner's representatives were not immediately returned on Sunday night.
Los Angeles Mayor Karen Bass called Reiner's death a devastating loss for the city.
"Rob Reiner's contributions reverberate throughout American culture and society, and he has improved countless lives through his creative work and advocacy fighting for social and economic justice," Bass said in a statement.
"An acclaimed actor, director, producer, writer, and engaged political activist, he always used his gifts in service of others."
The son of comedy legend Carl Reiner, Rob Reiner was married to photographer Michele Singer Reiner since 1989.
The two met while he was directing When Harry Met Sally and have three children together.
Reiner was previously married to actor-director Penny Marshall from 1971 to 1981.
He adopted her daughter, Tracy Reiner.
Carl Reiner died in 2020 at age 98 and Marshall died in 2018.
Killings are rare in the Brentwood neighbourhood.
The scene is about several kilometres from the home where O.J. Simpson's wife Nicole Brown Simpson and her friend Ron Goldman were killed in 1994.
- Reported with Associated Press