The video is as heartbreaking as the story. In it, a polar bear can be seen dazed and confused, twirling in circles just seconds before flopping into a nearby pool, thrashing, and then going still. Those, an amateur video claims, are the final moments in the life of Knut, a four-year-old celebrity polar bear that died Saturday at a Berlin, Germany zoo:

[Warning: Contains images that may be disturbing to some]

Knut’s sudden death on Saturday afternoon has many perplexed and worried, especially considering Polar bears usually live 15 to 20 years in the wild and even longer in captivity. That led animal rights activists to blame Knut’s “short and tortured life” on his captivity.

But animal and Knut lovers may finally be getting some answers, as the results of a necropsy, performed Monday, show brain problems contributed to Knut’s tragic death.

Initial findings by an institute in the German capital showed “significant changes to [Knut's] brain, which can be viewed as a reason for the polar bear’s sudden death,” the zoo said in a statement.

The zoo didn’t elaborate on the changes to the animal’s brain, and officials could not immediately be reached for further comment.

Pathologists found no changes to any other organs, the zoo said, adding that it will take several days to produce a final result. Further planned tests include bacteriological and histological, or tissue, examinations.

The video of Knut’s alleged final moments has sparked a controversy of its own. The website Jezebel originally posted it yesterday, only to scrub it hours later and see its editor-in-chief admit that it was a “mistake” to do so due to the shocking images.

Still, other sites have posted the video, including the New York Daily News, CBSNews.com, and even a Fox affiliate in Philadelphia.

Knut, who was born in December 2006 at the Berlin zoo, rose to celebrity status as an irresistibly cute, fluffy cub. Former Speaker of the House Newt Gingrich even visited him in 2007, posting a picture of the encounter online:

Heartbreaking Video: Knut the Polar Bears Final Seconds

Gingrich lamented Knut’s death on both his Twitter and Facebook accounts.

Knut was rejected by his mother at birth — along with his twin brother, who only survived a couple of days. He attracted attention when his main caregiver, Thomas Doerflein, camped out at the zoo to give the button-eyed cub his bottle every two hours.

The bear went on to appear on magazine covers, in a film and on mountains of merchandise.

Doerflein, the zookeeper who raised him, died in 2008 of a heart attack.

The zoo now wants to have Knut stuffed and put on display at Berlin’s Museum of Natural History, the German news agency DAPD reported.

It quoted a zoo spokeswoman as saying that the decision was made because Knut was a much-loved animal and officials wanted to make him available to science.

The Associated Press contributed to this report.