Maria Shriver is grieving the loss of a young life she says defies all logic.

The journalist and former first lady of California shared an emotional tribute Tuesday honoring her cousin Tatiana Schlossberg, who died at age 35 after a battle with terminal cancer. Schlossberg, the daughter of Caroline Kennedy, had publicly revealed her diagnosis only weeks earlier.

“I return to this space today to pay tribute to my sweet, beloved Tatiana, who left this earth today,” Shriver, 70, wrote in an Instagram post alongside a series of family photos. “I return to this space heartbroken because Tatiana loved life. She loved her life, and she fought like hell to try to save it.”

Shriver, who was previously married to actor and former California governor Arnold Schwarzenegger, did not attempt to soften the rawness of her grief.

“I cannot make sense of this,” she wrote. “I cannot make any sense of it at all. None. Zero.”

Schlossberg, an environmental journalist, was known for using her reporting to educate readers about climate change and environmental preservation. Shriver praised her cousin’s work, saying she “used her words to educate others about the earth and how to save it.”

The tribute also centered on Schlossberg’s family — particularly her mother.

“My heart has always been with my cousin Caroline ever since we were little kids,” Shriver wrote. “My entire being is with her now. What a rock she has been. What a source of love she has been.”

Shriver went on to list the family members who surrounded Schlossberg during her illness, including her husband George Moran, their children Eddie and Josie, and a wide circle of relatives, friends, and doctors who “tried so hard.”

In a portrait of the woman she lost, Shriver described Schlossberg as “the light, the humor, the joy.”

“She was smart — wicked smart, as they say — and sassy,” she wrote. “She was fun, funny, loving, caring. A perfect daughter, sister, mother, cousin, niece, friend. All of it.”

Shriver promised that Schlossberg’s children would grow up knowing who their mother was.

“Those of us left behind will make sure Eddie and Josie know what a beautiful, courageous spirit their mother was and will always be,” she wrote. “She takes after her extraordinary mother, Caroline.”

Schlossberg was diagnosed with acute myeloid leukemia, a rare and aggressive cancer affecting the blood and bone marrow, about a year and a half before her death. In November, she published a deeply personal essay in The New Yorkerdetailing her illness, motherhood, and confrontation with mortality.

In her tribute, Shriver urged followers to read the piece, calling it “extraordinary.”