T.J. Lane, 17, is currently being held as a juvenile, charged with three counts of murder, two of attempted murder and one of felonious assault, The (Cleveland) Plain Dealer reported. Juvenile Court Judge Timothy Grendell's decision allows Geauga County Prosecutor David Joyce to seek an adult indictment.
Lane faces a life sentence if convicted as an adult of aggravated murder.
Lane was arrested Feb. 27 in a wooded area about a mile from Chardon High School, located about 20 miles northeast of Cleveland.
Sheriff's Deputy John Bilicic testified Thursday that Lane told him when he was arrested: "I just killed a bunch of people."
"I don't really understand myself," he said when asked why he had done it.
Lane, who lived with his grandparents, was attending an alternative school program and took the bus from the high school every morning. He is accused of opening fire with a handgun in the high school cafeteria, killing three students and seriously wounding two others