ATLANTA (AP) — A 14-year-old Georgia boy indicted on murder charges in a mass shooting at Apalachee High School pleaded not guilty on Tuesday.

Colt Gray’s lawyer filed papers entering the plea after Gray was indicted on Thursday. They waived an arraignment hearing that had been scheduled for Nov. 21.

It’s common in Georgia for defendants to enter a plea and waive arraignment.

A Barrow County grand jury indicted Gray on a total of 55 counts as an adult, including murder in the deaths of four people and 25 counts of aggravated assault at the high school. Grand jurors indicted his father, Colin Gray, on 29 counts, including two counts of second-degree murder and two counts of involuntary manslaughter. Both also face multiple counts of cruelty to children.

Colin Gray had not yet entered a plea as of Tuesday and remained scheduled for his own Nov. 21 arraignment.

Colt Gray is being held in a juvenile detention center in Gainesville, while Colin Gray, 54, is being held in the Barrow County jail. Neither has sought to be released on bail, and their lawyers have previously declined to comment.

The Sept. 4 shooting killed teachers Richard Aspinwall, 39, and Cristina Irimie, 53, and students Mason Schermerhorn and Christian Angulo, both 14. Another teacher and eight more students were wounded, seven of them hit by gunfire.

Colin Gray is the first adult known to be charged in a school shooting in Georgia. His indictment is the latest example of prosecutors holding parents responsible for their children’s actions in school shootings. Michigan parents Jennifer and James Crumbley, the first to be convicted in a U.S. mass school shooting, were sentenced to at least 10 years in prison for not securing a firearm at home and acting indifferently to signs of their son’s deteriorating mental health before he killed four students in 2021.

Investigators have said Colt Gray carried a semiautomatic assault-style rifle onto a school bus, with the barrel sticking out of his book bag, wrapped up in a poster board. They say the boy carefully plotted the shooting at the 1,900-student high school northeast of Atlanta, drawing diagrams and listing potential body counts in a notebook. He left his second-period class and emerged from a bathroom with the rifle before shooting people in a classroom and hallways.

The shooting came as school officials and Colt Gray’s family had discussed enrolling him in counseling or even inpatient psychiatric treatment. His home life had long been unstable and investigators have said his mother, Marcee Gray, asked Colin Gray to secure his guns and restrict Colt’s access to firearms in the weeks before the shooting. Colin and Marcee Gray lived separately.

Jeff Amy covers Georgia politics and government.