A judge from the U.S. State of Ohio on Tuesday convicted a teen of killing three students in a school shooting spree last year and sentenced him to life imprisonment without parole, according to local media reports.

T.J. Lane, now 18, on Tuesday showed up at the courtroom wearing a white T-shirt with the word "killer" in capital letters, the same word police said he had emblazoned on the shirt he wore on Feb. 27, 2012 when he opened fired in a school cafeteria full of students, NBC reported.

Lane began a shooting rampage with a handgun while waiting for a bus from Chardon High school, east of Cleveland, Ohio, to the alternative school he attended, killing three students, aged 16 to 17, and injuring three others, said police reports.

Lane, who pleaded guilty to the charges last month, smiled and chuckled when he heard his sentence and the statements made by families of the victims. He even flipped his middle finger to people in the courtroom, according to a report by NBC affiliate WKYC.com.