Polar bears are famous for their snow-white fur and their playfulness. They live mostly in the Arctic circle and thrive in the cold environment.

When in closed spaces such as the zoo, their behavior can be observed through glass panels or large enclosures. What zookeepers witnessed in the Royev Ruchey Zoo in Krasnoyarsk was horrifying and unexpected when a male polar bear suddenly attacked an killed his female counterpart.

Aurora, the female polar bear, moved 1,900 miles from Krasnoyarsk in Siberia, to Izhevsk, the Urals to mate with the male polar bear, Baloo. During a two-week 'courtship' period, they played, swam, and basked in the sun together. At the time, Aurora appeared to be amenable to the set-up.

However, when the moment came for them to copulate, something went amiss. Andrey Gorban, the Head of Royev Ruchey Zoo in Krasnoyarsk, said that at the very moment Baloo mounted Aurora, something went wrong.

He added that when she showed her temperament, he became furious. In just seconds, he brutally attacked and killed the smaller female. The hostile attack is believed to be the first time such behavior is seen in polar bears in captivity.

Later on, zookeepers look back, thinking there was probably a clue of trouble ahead in their initial meeting. A video shows how Aurora inspected the male before turning her back on him and walking in the opposite direction.

Zoo staff threw water and shot a sedative at Baloo. According to the keepers, he fell beside her after the tranquilizer hit him, but Aurora was already dead.

The hostile attack is believed to be the first time such behavior is seen in polar bears in captivity. Polar bears have been known to kill cubs and weaker females in the wild for food, but never was it known for them to kill during copulation.

Gorban that they will carefully investigate the incident, both for themselves and for science. He adds that it was an unexpected outbreak of aggression.

Zoo officials were disheartened with what happened, as just a few days ago, they were reportedly happy that the two giants had found each other. Gorban said they even anticipated their offspring as they have already built enclosures meant for the little cubs.

A statement from Izhevsk Zoo said: 'The reason for the conflict between two recently completely peacefully coexisting polar bears Aurora and Baloo remains a mystery.'

Desperation- Driven Cannibalism

In the Arctic, when hunting becomes hard, some polar bears kill their young for food. The tragic occurrence, long known to the locals in the Arctic, has been studied since the 1980s. Scientists believe that polar bears eat cubs in the late summer and autumn, when seals, their usual prey, are at sea and less available.

In the summer of 2015 off of Canada's Baffin Island, a raw video of male to cub polar bear cannibalism was shot during a Lindblad Expeditions trip on the National Geographic Explorer.

In the video, it showed a slow-moving cub and his mother trying to get away from the large male chasing them. Once he reached the cub, he swiftly goes in for the kill, repeatedly biting the cub around the head and neck.

After failed attempts of rescuing her cub, the female swiftly retreats, cautious of becoming the male's next meal.

Jennifer Kingsley, who witnessed the event with her own eyes from aboard the National Geographic Explorer ship, said that it was hard to look away. She adds that although it was the reality of life in the Arctic, to actually witness it was really dramatic.