Kirk Douglas' daughter-in-law Catherine Zeta-Jones reacts to his death

Catherine Zeta-Jones is in mourning.

The "Chicago" star, 50, lost her father-in-law, Hollywood legend Kirk Douglas, on Wednesday when he died at the age of 103.

Zeta-Jones took to Instagram to share a message of love for her late family member.

KIRK DOUGLAS RECEIVES TRIBUTES FROM HOLLYWOOD STARS

"To my darling Kirk, I shall love you for the rest of my life," wrote the actress in the caption. "I miss you already. Sleep tight..."

In the black-and-white photo, Zeta-Jones plants a kiss on Douglas' cheek.

KIRK DOUGLAS: A LOOK BACK AT HIS RICH FAMILY LIFE

The actress has been married to Michael Douglas, his son, since 2000.

In December, Zeta-Jones shared a birthday message to Douglas on Instagram as well.

"This guy on my knee, is 103!!!!!" she wrote in the caption. "Happy Birthday Pappy!!! I love you with all my heart."

Michael, 75, also an actor, shared the news of his father's passing on Instagram on Wednesday.

CATHERINE ZETA-JONES AND LOOKALIKE DAUGHTER CARYS MODEL TOGETHER IN NEW FASHION CAMPAIGN

"It is with tremendous sadness that my brothers and I announce that Kirk Douglas left us today at the age of 103," Michael wrote on the platform. "To the world he was a legend, an actor from the golden age of movies who lived well into his golden years, a humanitarian whose commitment to justice and the causes he believed in set a standard for all of us to aspire to."

"But to me and my brothers Joel and Peter he was simply Dad, to Catherine, a wonderful father-in-law, to his grandchildren and great grandchild their loving grandfather, and to his wife Anne, a wonderful husband," he continued. "Kirk's life was well lived, and he leaves a legacy in film that will endure for generations to come, and a history as a renowned philanthropist who worked to aid the public and bring peace to the planet."

CLICK HERE TO GET THE FOX NEWS APP

The post concluded: "Let me end with the words I told him on his last birthday and which will always remain true. Dad- I love you so much and I am so proud to be your son."