Ethan Crumbley opened fire inside Michigan's Oxford High School on Tuesday, killing four of his fellow students.
Three students died in the shooting, while a fourth one succumbed to his injuries a day later. Seven others were injured.
Authorities say the shooting was premediated, so Ethan has been charged as an adult with 24 charges, including murder, terrorism, assault and weapons possession.
Ethan's parents, James and Jennifer Crumbley, have been charged with four counts of involuntary manslaughter. All three have pleaded not guilty and are locked up in the Oakland County Jail.