DETROIT (AP) — A teenager who was convicted of fatally shooting four students at his high school in Michigan is appealing his life sentence, his attorneys announced Friday.

Officials with the state Appellate Defender Office said in a statement that they have filed a request for Ethan Crumbley to be resentenced.

Crumbley, now 18, pleaded guilty to 24 charges, including one count of terrorism and four counts of first-degree murder, and was sentenced in December to life without parole. He was 15 at the time of the shooting.

His lawyers said new evidence shows seven witnesses could have testified about Ethan’s troubled childhood, his mother’s alcohol abuse during her pregnancy, and the potential impact of fetal alcohol spectrum disorder on Ethan, including how it could have stunted his maturation.

They said the evidence also raises questions about whether Ethan knew what he was doing when he pleaded guilty to the 2021 shooting at Oxford High School, and stressed that children can change.

“A life without parole sentence for a child is unconscionable,” the office said.

The Oakland County Prosecutor’s Office did not immediately respond to a message Friday seeking comment on the appeal.

Judge Kwame Rowe said during sentencing that the shooting was well-planned and Crumbley had plenty of time to stop as he walked through the school. The judge said he was especially troubled by how one victim was repeatedly shot and another was forced to watch as he shot a student at point-blank range.

The teen’s parents, James and Jennifer Crumbley, were convicted of manslaughter earlier this year after prosecutors accused them of allowing Ethan to access a gun, ignoring his mental health problems and declining to take him home when confronted with his violent drawings at school on the day of the attack.

They were the first U.S. parents to be convicted in a mass school shooting committed by their child.