A Rocky Mountain goat kid named Salix died unexpectedly on Saturday at the Denver Zoo.

According to a statement from zoo, animal care specialists observed the goat displaying abnormal behavior like a repetitive chewing motion and lethargy on Friday.

The zoo’s veterinary team immediately began emergency testing and closely monitored the kid overnight.

Sadly, the goat died the following day. As of Monday evening, the zoo has not yet determined the cause of death, but the incident is still under investigation.

Salix was born in May of this year, and was described by the zoo as “spunky” and “adorable”.

“In our profession, loss is inevitable, but this one really stings. I am heartbroken and confused. Salix was just a baby, and it doesn’t feel fair. When you get attached to the animals you care for, it makes losing them so much harder, but there is no way I could ever not love them. I’m proud to be a part of a team and a zoo that has such high standards of animal care, and I am at peace knowing that we did everything in our power to give him the best life possible,” said Animal Care Specialist Caitlin J.

The zoo hopes that further testing will help them better understand what happened.

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