The 14-year-old accused of fatally shooting four people at his high school in Georgia was expected to make his first court appearance Friday, a day after his father was also arrested for allowing his son to have a weapon.

According to arrest warrants obtained by The Associated Press, Colt Gray is accused of using a semiautomatic assault-style rifle to kill two students and two teachers at Apalachee High School in Winder, outside Atlanta. Nine people were also hurt in Wednesday’s attack. Authorities have not offered any motive or explained how Gray obtained the gun or got it into the school.