Ohio - For years, dog Dierks was his owner's everything, but then this "thing" came along!

Dierks was rescued from an animal shelter in Traverse City, Michigan, six years ago by his owner, Brin Engelhardt.

"Dierks and I did everything together and have a very close bond," she told Newsweek.

So, it could have all been so beautiful, but instead, Engelhardt made at least one fatal mistake – at least from her pup's perspective!

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"I met my husband, who Dierks adores, we moved to Ohio, and not long after we got married we found out we were having a baby," she explained.

The world fell apart for "only child" Dierks shortly after, as can be clearly seen in a TikTok video that quickly went viral!

The clip first shows the squeaky-clean baby Jae, with the dog sitting next to him.

The camera then pans to Dierks, who looks into the lens in downright horror!

The subtitle appropriately reads, "When you've been enjoying quiet cuddles for 6 years and then your parents bring this thing home."

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"'is there a return policy?' Pup is unimpressed," one user joked in the comments.

While TikTok users are having a great time with the curious video, which now has 4.5 million views and over 650,000 likes, Brin Engelhardt wants to make something clear.

"All jokes aside, Dierks loves being a big brother to Jae," she told the outlet.

So why does the dog in the video look so horrified at the camera? Engelhardt believes she knows the answer: "Dierks was used to being the only baby in the house for so long that he was very shocked at how loud a baby can be."

"Dierks was so used to being the only baby in the house for so long that he was very shocked at how loud a baby can be," she explained.