ATLANTA (AP) — A grand jury indicted both a father and son on murder charges Thursday in a mass shooting at Apalachee High School in Winder, Georgia.

A Barrow County grand jury indicted 14-year-old Colt Gray on a total of 55 counts, including murder in the deaths of four people and 25 counts of aggravated assault. Grand jurors formally charged his father, Colin Gray, with 29 counts, including two counts of second-degree murder and two counts of involuntary manslaughter. Both also face multiple counts of cruelty to children.

Both are scheduled to appear for arraignment on Nov. 21, when each would formally enter a plea. Colin Gray is being held in the Barrow County jail. Colt Gray is charged as an adult but is being held in a juvenile detention center in Gainesville. 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.

Second-degree murder is an unusual charge under Georgia law, resulting from a death of a child when someone is committing the crime of cruelty to children. Colin Gray, 54, is accused of committing cruelty to children by giving his son access to a gun and ammunition “after receiving sufficient warning that Colt Gray would harm and endanger the bodily safety of another,” the indictment states.

District Attorney Brad Smith told reporters on Sept. 6 that he had never before prosecuted a second-degree murder charge.

Thursday, Smith told reporters he charged Colt Gray with 25 aggravated assault counts for everyone at the school who was in the line of fire, although Colt Gray shot 11 people. The 20 cruelty to children charges against Colin Gray are for every child Colt Gray is alleged to have shot at.

“Every person, every kid in that school was a victim," Smith told reporters. “Kids in all the other schools that were locked down during this were victims. Parents that were terrified about where their kids were.”

Colin Gray’s 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 testified Wednesday during a preliminary hearing for Colin Gray that Colt Gray carried a semiautomatic assault-style rifle onto the school bus, with the barrel sticking out of his book bag, wrapped up in a poster board. They say the boy left his second-period class and emerged from a bathroom with the rifle before shooting people in a classroom and hallways.

Investigators have said the teenager carefully plotted the shooting at the 1,900-student high school northeast of Atlanta. A Georgia Bureau of Investigation agent testified that the boy left a notebook in his classroom with step-by-step handwritten instructions to prepare for the assault. It included a diagram of his second-period classroom and his estimate that he could kill as many as 26 people and wound as many as 13 others. "Surprised if I make it this far,” the boy wrote.

There had long been signs that Colt Gray was troubled.

Colt and Colin Gray were interviewed about an online threat linked to Colt Gray in May 2023. Colt Gray denied making the threat at the time. He enrolled as a freshman at Apalachee after the current academic year began and then skipped multiple days of school.

In an Aug. 18 electronic message seeking help from a counseling service, according to Wednesday testimony, Colin Gray wrote of his son: “We have had a very difficult past couple of years and he needs help. Anger, anxiety, quick to be volatile. I don’t know what to do.”

Investigators said Colt Gray had at least one “severe anxiety attack” during his short stay at school. A counselor said he reported having suicidal thoughts and rocked and shook uncontrollably while in her office.

Colt’s mother, Marcee Gray, who lives separately, told investigators that she had argued with Colin Gray in August, asking him to secure his guns and restrict Colt’s access. Instead, over time, he bought the boy ammunition, a gun sight and other shooting accessories, records show.

Colt Gray even created a “shrine” to school shooters over his home computer, Georgia Bureau of Investigation Agent Kelsey Ward said in court. When Colin Gray had asked his son who the people in pictures were, Ward testified, Colt told his father that one was Nikolas Cruz, the shooter in the 2018 massacre at Marjory Stoneman Douglas High School in Parkland, Florida.

Ward said Marcee Gray told her in an interview that Colt Gray's "fascination with guns had gotten very bad” over the past year. At one point, Colt asked his dad to buy him an all-black “shooter mask,” saying in a joking manner that, “I’ve got to finish up my school shooter outfit, just kidding,” Ward said.

Colt’s parents had discussed their son’s fascination with school shooters, but decided that it was in a joking context.

Colt Gray earlier asked his mother to put him in a "mental asylum,” and after the anxiety attack, the family arranged to take him on Aug. 31 to a mental health treatment center in Athens that offers inpatient treatment, but the plan fell apart when his parents argued about Colt’s access to guns the day before, and his father said he didn't have the gas money, an investigator said.

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Associated Press Writer Kate Brumback in Atlanta contributed to this story.