A 26-year-old man was arrested in Kandal province yesterday for beating his 50-year-old brother to death after catching him attacking their mother with a meat cleaver during an apparent fit of rage prompted by news he had been assessed by a doctor as mentally ill, police said.

Sa’ang district police chief Seng Socheat said the incident started at about 6:30am when Huot Samtech walked in on his brother, Huot Heng, attacking Khy Sok Him, 68, because he had become enraged after discovering a letter diagnosing his illness.

Samtech picked up a stick and used it to beat Heng on the head, the police chief said, killing him but saving the mother’s life. “The female victim was badly injured and admitted to hospital,” he added.

Chao Vuthy, chief of Kandal’s provincial serious crime office, said police also considered Samtech’s killing of his brother to have been committed in self defence, as his left hand was injured in the fight.

He said Samtech was being detained at the Sa’ang district police station while authorities prepare to forward him to the provincial police today for further interrogation.