(NewsNation) — Teenager Ethan Crumbley pleaded guilty Monday to terrorism and first-degree murder charges, nearly a year after the attack at Oxford High School in southeastern Michigan.

Crumbley pleaded guilty to all 24 charges, including murder and attempted murder, after a school shooting at Oxford High School. Crumbley was charged as an adult.

The prosecutor’s office said no deals were made ahead of Monday’s plea. A first-degree murder conviction typically brings an automatic life prison sentence in Michigan, but teenagers are entitled to a hearing at which their lawyer can argue for a shorter term and an opportunity for parole.

Crumbley’s parents are also facing trial on manslaughter charges. They’re accused of failing to intervene when Crumbley showed signs of mental health issues and giving their son access to the gun used in the shooting. It’s possible Crumbley could be called to testify on their behalf.

Parents of Oxford High students said the school failed to protect their children and the shooting could have been prevented.

The school discovered a disturbing note from Crumbley, which included a drawing of a gun, but sent him back to class after his parents refused to take him home. The families of six students have filed a lawsuit against the school for failing to follow protocol when dealing with Crumbley.

Multiple students have also filed a lawsuit against the school. They are demanding an investigation into the shooting and changes to the school’s security procedures, including not returning students to class if they are at risk of harming themselves or others.

The Associated Press contributed to this report.