An arrest warrant was issued Thursday for a 17-year-old boy from the town of Osafune, Okayama Prefecture, in connection with the previous day's fatal bludgeoning of his mother and an assault on four members of his high school baseball team, police said.
About 80 investigators are looking for the boy, whose whereabouts is unknown.
The woman, who was not identified, was found by her husband at around 5:40 p.m., bleeding from head wounds, investigators said. She was taken to a hospital but pronounced dead on arrival.
Earlier Wednesday, the school called police and said the boy had attacked several students with a baseball bat at around 4:35 p.m.