SAN DIEGO, Calif. (KSWB/KUSI) — Kris Jenner announced on social media Tuesday that her sister, Karen Houghton, died unexpectedly earlier this week.

ABC News reported that the San Diego County Sheriff’s Department responded to a call for medical aid at about 1:30 p.m. Monday. When deputies arrived, paramedics were already attempting lifesaving measures on Houghton, according to the outlet.

Houghton was reported dead in San Marcos in northern San Diego County, TMZ reported. The exact circumstances of her death are unclear. NewsNation affiliate KSWB has reached out to San Diego County officials for additional details.

In a post on her Instagram, the “Keeping Up With the Kardashians” star paid tribute to her sister.

“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. “Karen was beautiful inside and out. She was 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.”

Houghton was 65, three years younger than Jenner, who is 68, according to TMZ.

“Karen’s passing is a reminder that life is so short and precious and tomorrow is never promised. We must tell those we cherish how much we love them. I love you my beautiful sister,” Jenner’s post continued.