PONTIAC, Mich. (AP) — A teenager has pleaded guilty to terrorism and first-degree murder in a Michigan school shooting.

Four students were killed and more were injured in the shooting nearly a year ago at Oxford High School.

The investigation put an extraordinary focus on Ethan Crumbley's home life and the alleged role of his parents in the tragedy.

The 16-year-old Crumbley pleaded guilty Monday to 24 charges in the Oakland County court.

Ethan Crumbley. Jeff KowalskyAFP via Getty Images

On the day of the shooting, school staff discovered violent drawings and desperate messages created by Crumbley.

But his parents declined to take him home and he was allowed to stay in school.

James and Jennifer Crumbley are charged with involuntary manslaughter. They're accused of making a gun accessible at home and ignoring Ethan's mental health needs.

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