Halsey is grieving the loss of their dog, Jagger.

The “You Should Be Sad” singer took to their Instagram to reveal that their dog had passed away on Friday after suffering from a “progressive condition” called Myelomalacia.

Halsey, 27, noted that “this has been the worst week of my life” while reflecting on Jagger’s death in the Saturday post.

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Given that Jagger was on his deathbed, the singer mentioned how they expected him to be “old and rickety and grumpy,” but, “Unfortunately that is not how it happened for us.”

“Jagger was 5 years old and yesterday we lost him to a progressive condition called Myelomalacia. It is sudden and uncommon and unfair with a catastrophic prognosis,” they shared.

“Within three days, my beautiful baby boy went from chasing imaginary birds around the yard and laying in my lap turning his ears up at the sounds of Sesame Street, to having paralysis spread through his body by the hour. It was sudden and shocking and I still haven’t even really processed it,” Halsey continued.

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The singer adopted Jagger in 2017 when he was just “a few weeks old.” He was named after Mick Jagger and made frequent appearances on Halsey’s live streams, including some interviews. They even gave Jagger his own Instagram account that has gained over 10 thousand followers throughout the years.

In the heartbreaking tribute to their dog, Halsey explained that Jagger was their “very first love, who taught me how to be a mommy.” “My sweet, sarcastic, so very human boy … Every single person who had the privilege of meeting jagger will never forget him. He was that special,” they said.

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Halsey concluded the post by describing “the most visceral loss” they’ve ever felt.

“Like the absence of a vital appendage. Every single second of my day that once revolved around his little habits and routines is now full of just emptiness and silence,” they wrote. “If you loved Jagger along with me, thank you for giving him the best life the bestest boy could have ever had.”