Brooklyn, New York - He was sick, confused, and had hardly any time left, but the elderly dog named Zero got an incredible surprise in his final hours when his foster mom, Isabel Klee, chose to adopt him shortly before he would be euthanized.

Zero was an older dog from the shelter, suffering from illness and mental decline.

Isabel, who has been taking in foster dogs for years, knew that his case was different.

"We're just having a lot of conversations about Zero and his quality of life," she said in an emotional TikTok video.

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Zero was barking for hours and appeared visibly distressed, and his condition was deteriorating rapidly.

Then, Isabel had to make a tough decision.

"I've never had this happen before, so it's really hard for me to process that I couldn't help him and I couldn't save him," she explained.

But instead of letting Zero go as a foster dog, Isabel signed the adoption papers together with her partner Jacob.

"Jacob and I made the decision that before tomorrow, we are going to officially adopt him so that Zero can have a family before he passes," she explained.

The little family celebrated the adoption with a McDonald's ice cream and a cheeseburger – a final treat that the dog thoroughly enjoyed.

Days later, he crossed the rainbow bridge, surrounded by people who loved him.

"There will be no more pain, no more confusion, no more agitation, no more anger; just the legacy of a resilient little shelter dog who was loved until his very last breath," Isabel wrote in a subsequent TikTok.