Los Angeles, California - Karen Houghton, the sister of the Kardashians' momager Kris Jenner, passed away last month. New documents have emerged about her cause of death.

On March 19, Kris Jenner shared a collection of photos of her younger sister on Instagram, paying tribute and telling followers her sister had passed away "unexpectedly."

Now, TMZ has obtained a document that listed her cause of death.

Karen Houghton is said to have suffered a cardiac arrest and sudden cardiac arrhythmia. It also noted Type 2 diabetes.

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The document also revealed that the 65-year-old had bipolar disorder and was cremated.

"Karen was beautiful inside and out," Kris wrote after her sister's passing. "She was the sweetest, kindest, the most sensitive and vulnerable and so so funny."

"Karen’s passing is a reminder that life is so short and precious and tomorrow is never promised," she added. "We must tell those we cherish how much we love them."

Karen Houghton is the aunt of Kris' kids Kim Kardashian, Kourtney Kardashian, Khloé Kardashian, Rob Kardashian, Kylie Jenner, and Kendall Jenner.

Kim also honored her "Auntie Karen" in her own heartfelt post with throwback photos last month.