A 15-year-old boy was arrested Wednesday in western Japan for allegedly striking a woman in the head with a hammer the previous day, causing serious injuries including a skull fracture, police said.

The junior high school student, whose name is being withheld because he is a minor, told the police, "I hit her as she just happened to be there. I have wanted to kill a person for some time."

The boy, who was arrested on a charge of attempted murder, is suspected of striking Sumiko Nishiguchi, 70, on the head with a hammer several times on a street in Matsubara, Osaka Prefecture, at around 9:30 a.m. Tuesday.

The boy and Nishiguchi, who lives near the area, apparently did not know each other.

According to investigators, the father of the boy told the police that he believes his son was the assailant. The boy admitted to attacking the woman during questioning on a voluntary basis.

The father said his son has skipped school since around last summer.