A 5-year-old boy died and a 6-year-old boy was seriously injured Monday when they were crushed against a wall by a runaway truck in Ome, in the northwestern suburbs of Tokyo, police said.
Kanato Ishii, son of Yuji Ishii, 32, died from head injuries, police said.
Four children were waiting for a kindergarten bus at around 9:45 a.m. when the driverless truck, which was parked on a slope, rolled backward, crushing the two boys against a stone wall, police said.
Taiki Yamanaka, 30, the driver of the truck, was arrested on suspicion of professional negligence.
Yamanaka reportedly told investigators that he had properly applied the hand brake when he parked.
According to a witness, the truck started rolling backward shortly after the driver got out and rolled some 30 meters down the slope before hitting the children, police said.
The children were waiting for a bus of the privately run Fukushima Gakuen kindergarten in Ome.
A similar incident occurred in the same residential area a few years ago, when a runaway truck crashed into a building near the site of the accident.