Knut is dead: the famous polar bear at the Berlin Zoo has died suddenly and unexpectedly at age four.

Knut was wildly successful for his short life. After his mother, Tosca, rejected him shortly after his birth, Knut became a media darling and beloved surrogate child of a Berlin Zoo zookeeper, Thomas Dörflein. As a cub, Knut appeared on the cover of Vanity Fair magazine with Leonardo Di Caprio for an environmental issue.

The Berlin Zoo said that Knut collapsed and died suddenly in the water in his polar bear enclosure today. An autopsy will be performed to…