Chicago, Illinois - Krista Stoltenberg already knew that her three-year-old son Easton always looked for rainbows, but when he explained why, it broke her heart.

Stoltenberg didn't think much of her boy's obsession, until one day, Easton was visibly disappointed when a rainbow didn't appear.

"He didn't come to visit me," he announced sadly.

At that moment, a realization struck his mom like a bolt of lightning: Easton thought rainbows were visits from his old dog Odin, who had passed away recently.

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The 33-year-old shared the heartbreaking story in a TikTok video.

"The first question I asked my husband was, 'How am I going to tell him his best friend isn’t here anymore?'" Stoltenberg said, recalling taking her seriously ill dog to the vet to be put to sleep.

She added, "I knew that this was one of those pivotal parent moments that couldn’t be avoided. We needed to do the best that we could to get him through this grief process while also going through our own."

"Unfortunately, there's no rule book for how to explain death to a two-year-old. So we decided then that we would use something that a two-year-old could understand; the rainbow bridge."

Easton took his parents' explanation to heart and added his own twist: rainbows were a greeting from his deceased bestie.

Stoltenberg told Newsweek about the special connection her son had with Odin.

"They always gravitated toward each other. We have another dog that my son loves very much, too, but there was always something about Odin."