A 15-year-old boy in Yokohama has been arrested on suspicion of killing his mother and grandmother, investigators said.
The high school student went to the police Monday and said he stabbed the two with a knife at his home around 8 a.m. in a fit of rage after he was warned about school and studies. His name is being withheld because he is a minor.
The 50-year-old mother and 81-year-old grandmother were found dead from stab wounds in the family's home.
The boy showed up at a police station near their home in Totsuka Ward just before 1 p.m. Monday and told an officer that he "killed people," according to the Kanagawa Prefectural Police.
Asked who he killed, the boy said, "I stabbed my grandmother and mother" and produced a kitchen knife with a 17-cm blade out of a bag, the police said.
He reportedly said he turned himself in because he "committed a grave act."
Besides his mother and grandmother, the boy's family includes a 12-year-old sister, who was not at home at the time, and their 50-year-old father, who lives away from the family for work, according to the police.
The police said they believe the boy had no previous trouble at home or at school.
One of the boy's friends who knew him from elementary school said: "He got into fights and punched or kicked people, but he was never serious. He also liked talking to people."
The boy belonged to a track team when he was in elementary school and joined a judo team in junior high school, where he served as a captain, according to the friend and other sources.