Knut's last moments: Harrowing film of the death of the world's most famous polar bear emerges amid fears over his treatment

WARNING: Animal lovers will find this video extremely distressing, please do NOT view it if you are easily upset. We have chosen to include it because of the profound animal welfare issues raised by Knut's short life and and untimely death

This is the moment Knut, the world's most famous polar bear, died as he had lived his controversial life - in captivity and in front of a crowd of human spectators.

After compulsively turning in circles, he convulsed violently on his favourite rocky perch, let out a blood-curdling scream then fell dead into his enclosure's water pool.



The final, horrific moments of the world's most famous polar bear were captured on a tourist's video camera at Berlin Zoo on Saturday.



In the deeply harrowing film, spectators' whoops turn to screams as the realisation dawns that Knut's wild convulsions are not one of his usual playful performances.



Trauma: In the deeply harrowing film, spectators' whoops turn to screams as the realisation dawns that Knut's convulsions are not one of his usual playful performances

In obvious pain, he is shown repeatedly circling his own shadow, his left hind leg twitching uncontrollably, before he is overcome by a violent fit.

Moments later, the four-year-old bear lets out a gut-wrenching scream as he rises onto his haunches and lurches forward into a pool of water.

Although the cause of death has not yet been determined, serious concerns over his treatment at Berlin Zoo have already been raised.

No joke: In obvious pain, he is shown wildly circling his own shadow, his left hind leg twitching uncontrollably, before he is overcome by a fit of convulsions

Death throw: Moments later, the four-year-old bear lets out a blood-curdling scream as he rises onto his haunches and falls dead into a pool of water

Initial theories were that the four-year-old polar bear suffered a heart attack or stroke. But animal rights groups have condemned the way he had been reared in the zoo, blaming the stresses of his ‘unreal’ celebrity-style life for his early death.



Polar bears normally live for 15 to 20 years in the wild and often longer in captivity. But animal rights campaigners fear Knut had become psychologically unbalanced, dependent on crowds — a highly unnatural state for a polar bear — and unable to mix with other bears.



Animal rights group PETA slammed the zoo for what it said was 'intensive' breeding of polar bears in zoos and claimed putting him in an enclosure with three females led to 'enormous stress'.

A young girl prepares to leave her tribute to Knut, made up of flowers and a toy bear, outside the polar bear's enclosure in Berlin

Concerns have also been raised that he was being bullied by the three female bears he shared the enclosure with - Tosca, Nancy and Katjuscha. A spokesperson said: 'PETA Germany repeatedly asked zoo authorities to move Knut away from the three females to a different location. His premature death could possibly have been avoided. Polar bears don't belong in captivity.'

On Sunday, crowds gathered beside his empty compound, laying down red roses and white stuffed polar bears, lighting candles and putting up pictures of Knut with personal messages for him.

Fans of the polar bear leave flowers next to the enclosure where he died yesterday. Knut was Germany's best-loved and biggest animal star. A keeper found the four-year-old's body floating in the pool in his enclosure. It is unclear as to why he died

Cute: Knut pictured shortly after his arrival at the zoo four years ago (left) and making a splash (right) last year

'I can't comprehend what happened there. He was happy before, there were no signs of anything - it's so shocking,' said fan Eveline Litowski, who said she had come to the zoo to find out more about Knut's early death.



Litowski was among a crowd of fan's at Knut's empty compound this morning who laid down white roses, lit candles or put up pictures of Knut with personal messages for the bear - and speculated on the cause of his death.

Some fans already had their own theories. Nadine Hipauf said she worried somebody may have poisoned Knut - whether on purpose or not.



'My biggest fear is that somebody may have thrown something in for him to eat,' she added.

Others claimed that Knut had died of stress, saying he was bullied by the three female bears he shared the enclosure with - Tosca, Nancy and Katjuscha.



Playtime: dozens of people look on as Knut wrestles with a bag

'They should have given him a compound of his own,' said pensioner Brigit Krause. 'The ladies were constantly harassing him.'

His rise to fame started after he was rejected at birth by his mother. He would have died had the zoo not taken the decision to rear him by human hand.



Keeper Thomas Doerflein moved in with him at the zoo, feeding him at night and changing nappies on him.



Soon, visitors from far and wide came to watch twice-daily shows as the keeper played with this enchanting tiny ball of white fluff. Soon, he featured on the front cover of Vanity Fair — alongside actor Leonardo DiCaprio — and made an estimated £6 million for the zoo through the marketing of pictures, key chains, sweets and stuffed Knuts.



But the special bond with his keeper was broken in September 2008 when Doerflein died from a heart attack. It was widely speculated he died from a broken heart after being banned from entering Knut’s enclosure because the zoo authorities were concerned the bear had grown and was too dangerous.



However, it seemed Knut in turn had become depressed — seemingly distracted and looking lost if there were no crowds around. At this point, animal psychologists warned he was in danger of becoming a ‘psycho bear’.



Match-making: Knut cuddles at Berlin Zoo here with Gionvanna. But the two never mated and the other potential mates bullied him

A suggested solution was to put him in with three females — Tosca, Katyusha and Nancy — in an attempt to normalise his life. But the trio ganged up on Knut, biting and chasing him away.



‘He was not sick. We don’t know why he died,’ said his keeper, Heiner Kloes.



Knut’s premature death plunged Berlin into gloom. ‘His death is awful,’ said the city’s mayor, Klaus Wowereit. ‘He was the star of Berlin Zoo.’



‘I’ve been crying nonstop since I heard about his death,’ said Ingrid Rommel, a 65-year-old widow from Berlin, who said she had been visiting Knut weekly since his birth on December 6, 2006. She credited him with helping her get over the death of her husband.



Heidemarie Vogel, 58, remembered that Knut had sometimes raised his paw when she called over to him.



‘It was as if he was waving to me — so nice,’ she said tearfully.