A tiger was mauled and killed by another tiger at a Winnipeg zoo Thursday morning after staff mistakenly left a gate unlocked.

Winnipeg’s Assiniboine Park Zoo has confirmed that Baikal, a 19-year-old male Amur tiger, was killed Thursday morning.

“Baikal passed away this morning following an incident involving one of the zoo’s young male tigers,” said Margaret Redmond, president of the Assiniboine Park Conservancy.

“This involved an internal gate between enclosures, and at no time were zoo visitors in any danger,” she told CTV News.

The zoo says Baikal left his enclosure Thursday morning and entered another area where two younger male tigers were being housed. Baikal was then attacked and killed.

The Assiniboine Park Zoo says tigers are territorial animals, and it’s not unusual for them to react violently to an intruder in their space.

Baikal was in Winnipeg on loan from the Toronto Zoo.