Chardon High School shooter TJ Lane pleads guilty (VIDEO)

Teenager TJ Lane pleaded guilty today to charges he gunned down three classmates at Ohio's Chardon High School last year.

Lane, 18, pleaded guilty in Geauga County court to aggravated murder, attempted aggravated murder and felonious assault in the attack last February, The Plain Dealer reported.

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His sentencing is scheduled for March 19.

Last October, Lane originally entered a plea of not guilty by reason of insanity.

His appearance in court today came one day before the anniversary of the shootings at Chadron High school that left three students dead and three more injured, according to The Associated Press.

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Prosecutors say Lane took a .22-caliber pistol and a knife to the school last Feb. 27 and sprayed bullets at a group of students in the cafeteria.

According to investigators, Lane has admitted to the shooting and believed he had "killed a bunch of people," but doesn't know why he did it, WEWS reported.

Danny Parmertor, Russell King Jr. and Demetrius Hewlin died as a result of the shooting. Three more students, Nick Walczak, Nate Mueller and Joy Rickers, were injured.

Earlier this month, Mueller traveled to Washington, DC, as part of a group urging Congress to pass gun control legislation, Reuters reported.