Police questioned a man Saturday morning in Gunma Prefecture on suspicion of professional negligence resulting in the death of a 10-year-old boy, police said.
The police said they received a report around 9 p.m. Friday of a man fleeing the scene of a car crash carrying a boy. The man's car had crashed into a guardrail in the town of Sakai in the prefecture.
No one was in the car when police arrived, but a man appeared with a child at a hospital in the prefectural city of Isesaki around 11 p.m., the police said.
The police said the man disappeared after he told hospital staff to take care of the child and to contact his parents.
The boy was declared dead from posttraumatic shock. The police identified him as third-generation Japanese-Brazilian Erick Gabriel Yokoyama, a fourth grader at an Isesaki elementary school.
The police said they found the man in his apartment Saturday morning and persuaded him to be questioned voluntarily.
The man denied the allegations, they said.
According to police investigations, the man is the boy's soccer coach and a friend of his parents.
At the time of the accident, the man was taking Yokoyama to a shopping center with his parents' permission, the police said.