ANCHORAGE (AP) — A beloved polar bear at the Alaska Zoo in Anchorage has died.

A zookeeper Sunday found Ahpun, who was about 20 years old, dead during morning rounds.

Zoo director Patrick Lampi says Ahpun had shown no signs of illness and a necropsy found no cause of death.

Tissue will be sent out for additional analysis.

Ahpun was orphaned in 1998 near Point Lay on Alaska’s northwest coast. A man returning from a fishing trip unknowingly approached a den and Ahpun’s mother charged.

The fisherman shot the bear in self-defense and determined she had emerged from a den. The fisherman crawled inside and found the cub.

Ahpun grew from a 31-pound cub into a 700-pound adult.

The zoo also has a male polar bear, nicknamed Louie.