GREENSBURG, Pa. — A young man who pleaded guilty to stabbing 20 fellow students and a security guard at his suburban Pittsburgh high school when he was a teenager says his prison sentence is too long.

Alex Hribal’s defense attorney Pat Thomassey says in a filing made Friday the facts of the case do not support Hribal’s 23 1/2- to 60-year sentence.

The Tribune Review reports Thomassey says the sentence imposed last week should be reduced to 15 to 30 years.

Hribal pleaded guilty in October to a weapons charge and numerous attempted-homicide and aggravated-assault charges. He was 16 when he used two 8-inch (20-centimeter) kitchen knives to stab and slash his way through the hallways of Franklin Regional High School in Murrysville in 2014.

Four students were critically injured but survived.

Information from: Tribune-Review,