Pictures: Knut through the years
Berlin's beloved polar bear Knut died alone in his compound at the age of four on March 19, 2011. He was hand-raised by zoo keepers after his mother rejected him at birth. "He was by himself in his compound, he was in the water, and then he was dead. He was not sick, we don't know why he died," said bear keeper Heiner Kloes.
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