One of the polar bears living at Assiniboine Park Zoo passed away on Monday.

The zoo said Blizzard, a five-year-old bear, began experiencing a loss of appetite and lethargic behaviour about two weeks ago. The veterinary team decided to anesthetize him in order to conduct a full assessment of his condition, and prescribed him oral antibiotics.

According to the zoo he was monitored carefully and was doing well up until this past weekend, when his condition appeared to take a turn for the worse.

The veterinary team decided to anesthetize him once again in order to re-assess his condition. Officials said the procedure went well, however while reversing the anesthesia Blizzard experienced respiratory distress.

The zoo said staff did everything they could to save him, but he passed away.

“It is always a sad day when we lose one of the beloved animals at the Zoo, but a loss under these circumstances is particularly challenging. Blizzard was a beautiful bear and he will be dearly missed by Zoo staff, visitors, and volunteers,” said Dr. Chris Enright, the zoo’s director of veterinary services, in a news release.

An investigation into his cause of illness is preliminary. The zoo said a necropsy was conducted Monday evening and early results show signs of inflammation, fluid in the chest cavity, and some abnormalities in the heart.

Blizzard had been living at the Assiniboine Park Zoo since September 2014 when he and his sister Star were transferred there after being spotted without their mother as cubs.