A 15-year-old boy arrested for the fatal stabbing of an elderly woman in the city of Chiba told police he wanted to be sent to a juvenile detention center to escape his troubled home life, according to investigators.

The suspect, a junior high school student living in the city’s Wakaba Ward, allegedly attacked 84-year-old Yayoi Takahashi from behind with a knife at around 5 p.m. on Sunday. Takahashi died from traumatic shock after suffering multiple stab wounds to her back, including two that pierced her lungs and one that reached her heart, police said.

An autopsy revealed all of Takahashi’s wounds were concentrated on her back, with no defensive injuries — suggesting the attack came without warning.