A beloved hippo was beaten and killed inside his exhibit at El Salvador’s National Zoo in an attack authorities condemned as “cowardly and inhumane.”

The 15-year-old animal named Gustavito died Sunday, days after he was found slashed and stabbed by unknown attackers, officials said. He sustained “multiple blows on different parts of the body” from “blunt and sharp objects,” El Salvador’s Ministry of Culture said in a statement to CNN. The Ministry and Zoo director Vladen Henríquez said Gustavito had bruises, puncture wounds and cuts on his head, body and feet and inside his mouth.

Zookeepers discovered the hippo’s wounds last Thursday after he finally emerged from his pool following days hidden from sight. Officials believe he was beaten late Tuesday, according to CNN.

Details surrounding the attack and Gustavito’s cause of death remain unclear. The incident, which is under investigation, has sparked national outrage. “They killed an animal that only entertained us,” Martin Castillo, an El Salvador street vendor, told the Associated Press.

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