Animal rights activists in Italy have called for tougher penalties against animal cruelty after a rescue dog that saved people in a major earthquake was poisoned and killed.

Kaos, a German shepherd, was hailed Italy’s “hero dog” after finding survivors buried beneath the rubble in the hours after a 6.2-magnitude earthquake struck the hilltop town of Amatrice in central Italy in August 2016, killing 230 people. Alongside his owner, Fabiano Ettore, Kaos was among the first to arrive at the scene and worked relentlessly over the next few weeks to assist rescue workers.

Ettore found his poisoned body in the garden of their home in Sant’Eusanio Forconese, a town in L’Aquila province, on Saturday.

“I have no words,” Ettore said. “I can’t understand such a horrible act. He was alive at least until two o’clock in the morning, as I heard him bark.”

Animal rights activists lambasted his killer as a “dangerous criminal” while calling for more severe penalties against those who mistreat and kill animals.

“They killed the hero who, together with rescuers, dug with his four paws during those dramatic hours to find survivors of that massacre,” said Rinaldo Sidoli, a communication manager for Animalisti Italiani.

“Kaos saved humans, and those same humans poisoned him.”

Kaos, born in Rome in early 2015, also assisted rescuers in a subsequent earthquake in Norcia in late October 2016. The Norcia quake was Italy’s most powerful in a decade, but no lives were lost. More recently, he helped to find a missing man.

“We will not rest until justice is done,” said Sidoli. “We must push the political world towards a new law that foresees more severe penalties for those who mistreat and kill animals.”

Ilaria Fontana, a politician with the Five Star Movement, which is governing Italy alongside the far-right League, said: “We will find those responsible. It is unacceptable and those who do not respect animals will pay.”

Italian police have opened an investigation into the suspected poisoning.