The polar bear rose to global fame after he was rejected by his mother when he was born in captivity on December 5, 2006...
But tragedy struck again before Knut's second birthday in 2008, when Mr Dorflein [who cared for him] died of a sudden heart attack at the age of 44.
Observers noted that the bear appeared to suffer from depression in the weeks after his beloved keeper and constant companion died.
Experts had earlier warned that the Knut was developing into a 'psychopath' who was too dependent on human contact.
In 2009 Knut was the subject of a bitter custody battle between two zoos. Neumuenster Zoo had loaned Berlin Zoo Knut’s father Lars in 1999 on the condition that the first-born cub from his union with mother Tosca would belong to Neumuenster.
Experts are currently performing an postmortem examination.
