Kate Cassidy pens emotional note to late boyfriend Liam Payne: 'The love of my life'

Kate Cassidy shared an emotional note to late boyfriend Liam Payne a week after the One Direction singer's tragic death.

"I don't even know where to begin. My heart is shattered in ways I can't put into words," Cassidy wrote in an Instagram post shared Wednesday, Oct. 23. "I wish you could see the huge impact you've had on the world, even as it feels so dark right now."

Cassidy said Payne "brought so much happiness and positivity to everyone—millions of fans, your family, friends, and especially me," adding that he's "so incredibly loved."

"You are—because I can't say were—my best friend, the love of my life…," she wrote. "None of this feels real, and I can't wrap my head around this new reality of not having you here. I'm struggling to figure out how to live in a world without you by my side."

Cassidy said Payne had "the kindest soul and the most fun-loving spirit," adding that it feels "like I've lost the best part of myself" and that he "brought so much light into my life."

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The couple, who had been linked since 2022, were planning their future together, Cassidy then revealed.

"A few weeks ago, we sat outside on a beautiful evening manifesting our lives together," she wrote. "I keep your note close, even though you told me not to look at it. It said, 'Me and Kate to marry within a year/engaged & together forever 444.'"

"Liam, I know we'll be together forever, but not in the way we had planned. You'll always be with me. I've gained a guardian angel," she concluded her post. "I will love you for the rest of my life and beyond, carrying our dreams and memories with me everywhere I go."

Payne died at age 31 on Wednesday, Oct. 16, after falling from the third floor of his hotel room in Argentina, according to state police.

The "Strip That Down" singer's body was found in the inner courtyard of the hotel, where he was pronounced dead on the scene.

Results from Payne's autopsy are still yet to be revealed, but a partial autopsy found that he had multiple substances in his system at the time of his death, sources told ABC News.

Sources also told ABC News that Payne's body will remain in Argentina until the autopsy is complete.