Kris Jenner announces sister Karen Houghton has died: 'I love you my beautiful sister'

Kris Jenner announced in an Instagram post Tuesday that her sister Karen Houghton had died.

The San Diego County Sheriff's Department confirmed to ABC News that Houghton, 65, died Monday. Media relations director Lt. David LaDieu said deputies responded to a "medical aid call for service" at approximately 1:28 p.m. local time and arrived to the Carlsbad Fire Department "providing lifesaving care to a patient."

The cause and manner of death were not immediately clear.

ABC News has reached out to Jenner's representatives for additional confirmation and comment.

In her Instagram post Tuesday, Jenner wrote, "It is with the heaviest heart and deepest sadness that I share that my sister Karen passed away yesterday unexpectedly."

Jenner expressed grief over her younger sister's death in the lengthy Instagram post, in which she extended condolences to Houghton's daughter Natalie, as well as her own mother.

Houghton and Jenner are the children of Mary Jo ("M.J.") Campbell and Robert True Houghton.

"My heart aches for my mom MJ and my niece Natalie and I pray that God guides us all through this difficult time," Jenner wrote.

Jenner remembered her sister as "the sweetest, kindest, the most sensitive and vulnerable and so so funny."

"She always felt grateful and thankful for her life and treasured her family and friends and especially her beautiful daughter," she wrote. "She holds such a huge part of my heart and I cherish every single memory we have together."

Houghton, who kept a low profile compared to her celebrity family members, was three years younger than Jenner, who is 68.

The "Keeping Up With the Kardashians" star finished her post with a reminder to her followers to appreciate moments shared with loved ones.

"Karen's passing is a reminder that life is so short and precious and tomorrow is never promised," she wrote. "We must tell those we cherish how much we love them. I love you my beautiful sister."