A mentally ill man was arrested on Wednesday in Kampong Cham province over the brutal killing of his 3-year-old nephew, according to police.

Yem Sophal, Kampong Cham deputy police chief, said villagers and police had long been aware of the issues of Huon Sarom, 38, who had been chained in a shack behind his family’s house for years. After breaking free on Wednesday afternoon, Sarom argued with his brother and grabbed his young nephew, according to Sophal.

“While the father approached him, he used an axe to hack the boy many times in his head and back and body – he wanted to kill the father because he had been chained for about four to 10 years,” he said. Sophal said Sarom also tried to attack villagers but they threw rocks at him and knocked him down.

Chaining up the mentally ill for their protection, or the protection of others, is not uncommon in Cambodia, where mental health services are sorely lacking. A programme run by the Transcultural Psychosocial Organization (TPO) to unchain family members has had some success, but Chhim Sotheara, director of TPO, said long-term solutions are still needed.

“So many patients cannot afford to travel to receive treatment there,” he said. “There are mental health services in some health centres, but the quality is not sufficient to treat chronic and complicated patients.”

James McCabe, of the Child Protection Unit, called the killing “horrific and tragic” due to the innocence of the victim and the difficulty in treating the mentally ill in the Kingdom, adding that “due to his mental state, it is unlikely [Sarom] will be prosecuted”.