(CNN) -- A zoo and a nation mourned the death of a beloved animal friend on Monday.
Knut the polar bear captured the hearts of the German people, the media and the world, after he was abandoned by his mother at Zoo Berlin in 2007. A zookeeper hand-raised the cub until he was old enough to fend for himself.
The famous polar bear died unexpectedly Saturday in the zoo's polar bear enclosure.
"This bear not only charmed the people of Berlin but also won hearts around the whole world," Frank Bruckmann, chairman of the Zoo Berlin supervisory council, said Sunday.
"Knut was something very special," said Gabriele Thoene, a zoo board member.
The zoo spokesperson said a necropsy will be performed to determine the cause of death of the four-year-old bear.
A memorial fund has been opened in honor of Knut, with funds going toward the preservation of polar bear habitats.