Admitted Chardon shooter TJ Lane changed his plea to guilty during a hearing Tuesday morning.
Lane entered a guilty plea to all six counts - three counts of aggravated murder, two counts of attempted murder and one count of felonious assault all with firearms specifications.
Lane had previously pleaded not guilty by reason of insanity.
Prosecutors say on Feb. 27, 2012, Lane entered the cafeteria at Chardon High School and opened fire.
17-year-old Russell King, Jr., 16-year-old Daniel Parmertor and 16-year-old Demetrius Hewlin were killed in the shooting. 17-year-old Nick Walczak remains paralyzed from the waist down. 18-year-old Joy Rickers and a 6th, unidentified victim were treated and released from the hospital.
Lane was recorded in a police cruiser after he was picked up and read his rights saying, "I shot people." An officer asked why and he responded "I don't know."
Lane cannot be sentenced to death. He was under the age of 18 at the time of the deadly shooting, and turned 18 on Sept 19 of last year.