PITTSBURGH (AP) — A man charged with stabbing 20 fellow students and a security guard at his suburban Pittsburgh high school three years ago will spend the weekend considering whether to plead guilty, his attorney and a prosecutor said Friday.

The development grew out of a pretrial hearing Friday in Westmoreland County for 20-year-old Alex Hribal, who was 16 when he slashed his way through the hallways of Franklin Regional High School in Murrysville before classes began on April 9, 2014. Four students were critically injured and one required a liver transplant, but all survived and have since recovered.

If Hribal enters a general guilty plea next week to 21 counts each of attempted homicide and aggravated assault, plus a weapons charge, he'll likely face decades in prison. Common Pleas Judge Christopher Feliciani would determine Hribal's sentence, based on a presentence report on Hribal's background and other factors.

The defense acknowledges that Hribal committed the slayings and has unsuccessfully sought to get him declared legally insane.

District Attorney John Peck said he previously offered Hribal a 30- to 60-year prison sentence in return for a guilty plea, but Hribal rejected it.

Hribal's attorney Patrick Thomassey confirmed Friday that his client was considering a guilty plea, but he declined to discuss details.

Thomassey will advise the court of Hribal's decision on Monday, and a plea hearing could be scheduled for Tuesday. If not, Hribal's trial will begin Nov. 13.

Thomassey said last week that there was a "good chance" the charges would be resolved before trial.

Psychiatrists for both the defense and prosecution have testified Hribal purposely carried out the attack on the birthday of Columbine killer Eric Harris, whom Hribal "worshipped." Hribal first hoped to commit the attacks on the 15th anniversary of the Columbine massacre but couldn't because school wasn't in session that day, they said.

The judge in February rejected Hribal's request to plead guilty but mentally ill to the crimes. Had Hribal been allowed to enter that plea, he would have begun a prison term in a mental hospital, then would have been transferred to prison if doctors ever deemed him cured.