A 17-year-old male was arrested Thursday for allegedly hitting a 4-year-old boy on the head with a hammer in a park in Higashi Osaka, Osaka Prefecture, police said.
Shota Nishizu suffered a fractured skull and was being treated in a hospital, they said.
The teen, whose name has been withheld because he is a minor, is suspected of hitting Nishizu at around 3:40 p.m. while he was playing in the park.
The suspect, who is not in school and is not working, then walked to a nearby police station about 20 minutes later, carrying the hammer believed used to hit the boy, as well as a butcher knife, a kitchen knife, a stun gun and an ice pick.
"I am sorry. I hit a boy on the head with a hammer," the suspect was quoted by police as saying at the station reception desk.
He was arrested on suspicion of attempted murder, police said.
"I wanted to kill someone. It didn't matter who as long as the victim was not elderly. I had been thinking (about doing it) for about two years," the 17-year-old was quoted as saying by police.
The youth apparently did not know the boy, police said.