Today a necropsy, or animal autopsy, found that brain changes may have killed Knut, the Berlin zoo's beloved 4-year-old polar bear.
The zoo said in a press release:
"The preliminary results show distinctive anomalies at the brain, which could be seen as the cause of the ice bear's sudden passing ... Other irregularities on the organs could not be found from the pathologists."
Animal rights activists are accusing the zoo of causing Knut's death by failing to notice his strange behavior over the past few weeks. Thomas Schröder, director of the German Animal Welfare Association, told Time:
"Knut was subjected to enormous stress, not just by the media hype and public scrutiny, but also by the fact that he was kept in an enclosure with three females ... Polar bears tend to be loners ... Knut was looking apathetic, he lay in a corner of his enclosure - someone should have picked up on this."
Heiner Klös, who cared for Knut since he was born, says that it's normal for polar bears to be placed together in zoos and, "He had a fantastic experience and he was growing quickly and he showed absolutely normal behavior of a polar bear." The necropsy isn't complete, but he says of today's findings, "We are absolutely sure there was no stress and no heart attack, and no broken heart, if it's possible to find something like this."