Alonissos, Greece - Animal rights activists and fans are horrified and stunned at the cruel killing of Kostis, a symbolic animal of the Greek island of Alonissos. Now authorities are fervently searching for the culprit.

Kostis, the rare Mediterranean monk seal, got its name from a fisherman named Kostis, who rescued it off the coast of Greece during a storm in 2018.

A seal rescue organization then cared for the pup for months, and Kostis later became the island of Alonissos' symbol.

Now, the seal has been mysteriously murdered.

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According to enviornmental conservation organization MOm, Kostis was "executed at close range with a spear gun."

Dimitris Tsiakalos, spokesperson of the charity, told the BBC the animal was probably killed from an assailant on a boat.

The Mediterranean monk seal is an endangered and protected species. There are less than 700 in the wild, with almost half living in Greece.

The seal's death has caused outrage on social media, with users calling for the killer to be brought to justice.

Authorities have launched a full investigation and are offering 18,000 euros, or $21,260, as a cash reward to anyone with information leading to an arrest.