Rest in peace, Katherine Helmond. 

The Who's the Boss? star died at her Los Angeles home on Saturday, from complications from Alzheimer's, her agency, APA, confirms to ET. She was 89. 

 

In a statement to ET, Helmond's husband, David Christian, mourned the loss of his wife. "She was the love of my life," he said. "We spent 57 beautiful, wonderful, loving years together, which I will treasure forever. I’ve been with Katherine since I was 19 years old. The night she died, I saw that the moon was exactly half-full, just as I am now… half of what I’ve been my entire adult life. “

Alyssa Milano, who played Helmond's daughter on Who's the Boss?, also took to Twitter to pay tribute to the actress. 

"Katherine Helmond has passed away," she wrote alongside a photo collage. "My beautiful, kind, funny, gracious, compassionate, rock. You were an instrumental part of my life. You taught me to hold my head above the marsh! You taught me to do anything for a laugh! What an example you were! Rest In Peace, Katherine."

Helmond, best known for playing Mona Robinson on Who's the Boss?, was nominated for seven Emmys throughout her career. She also starred as Jessica Tate on ABC's daytime-serial spoof Soap, Doris Sherman on the network's Coach, and Lois Whelan, the mother of Patricia Heaton's character on Everybody Loves Raymond. 

The actress also had a successful film career, appearing in three Terry Gilliam movies: 1981's Time Bandits, 1985's Brazil and 1998's Fear and Loathing in Las Vegas. 

Helmond is survived by her husband, Christian, her half-sister, Alice Parry, and many much loved nephews and nieces. Helmond and Christian met at The Hampton Playhouse Summer Stock Theater, where he was the set designer, and she was the star. They married in 1962. A memorial for family and friends is being planned for the near future.