The 15-year-old who shot and killed four people at a high school in Michigan will be reportedly charged as an adult.

Ethan Crumbley was arrested on Tuesday after he brought a handgun to Oxford High School and opened fire on fellow students, killing four and injuring several others.

Oakland County Prosecutor Karen McDonald reported that while Crumbley is only 15-years-old, there was “undeniable” evidence that the act was remediated.

Some reports indicate that Crumbley posted a countdown to the shooting on an Instagram post hours before it occurred and used a gun his father recently purchased.

Crumbley is facing one count of terrorism, four counts of first-degree murder, seven counts of assault with intent to murder, 12 counts of possession of a firearm in the commission of a felony.