A 14-year-old boy and his father were charged with murder on Thursday following a grand jury indictment related to last month’s fatal shooting at a Georgia high school. The boy is accused of committing the attack, while his father is alleged to have provided him with the rifle used in what has become the deadliest school shooting in Georgia’s history.

The indictment lists numerous charges connected to the September 4th shooting at Apalachee High School in Winder, Georgia, where authorities say the boy, Colt Gray, fatally shot two students and two teachers. At least nine other individuals were injured in the incident.

Authorities have stated that Colt’s father, Colin Gray, who was arrested the day after the shooting, bears some responsibility because he gave his son access to the AR-15-style weapon used in the attack. They revealed that the gun had been a Christmas gift to his son.

According to the indictment, Colt Gray now faces a total of 55 charges, including counts of malice and felony murder, involuntary manslaughter, and child cruelty. His father, Colin Gray, 54, is facing 29 charges, including second-degree murder, involuntary manslaughter, and child cruelty.

The charges against Colin Gray reflect a growing legal approach where prosecutors are increasingly holding parents criminally accountable in cases where their children are involved in mass shootings. Earlier this year, the parents of the shooter responsible for the 2021 Oxford, Michigan school shooting became the first parents convicted in such a case. They were sentenced to 10 to 15 years in prison for involuntary manslaughter.

Lawyers representing the Grays were unavailable for comment on Thursday.

The indictments came after a preliminary hearing on Wednesday, during which investigators provided new insights into how Colt Gray allegedly planned and executed the attack. They also discussed warning signs of Colt’s distress in the weeks leading up to the shooting.

One investigator recalled an incident in the school counselor’s office where Colt Gray was reportedly rocking uncontrollably. Investigators also mentioned that Colt’s mother had been aware of her son’s growing fixation on school shootings and their perpetrators. Colt had even created a “shrine” featuring a photo of the gunman who killed 17 people at a high school in Parkland, Florida, in 2018.

On the morning of the shooting, Colt reportedly texted his mother, apologizing, before arriving at school with the rifle concealed inside a rolled-up poster board, sticking out of his backpack.

After the attack, investigators discovered a notebook left by Colt in his first-period classroom, where he had sketched the school’s layout and written estimates of how many people he could kill or injure during the shooting spree.

In the hallway, Colt predicted, “I’m thinking three to four people killed. Injured? Four to five,” according to testimony from a Georgia Bureau of Investigation special agent, who read from the notebook.

Colt estimated that he could kill as many as 15 to 17 people in one classroom and several more in a second. However, he wrote in parentheses beside these estimates, “Surprised if I make it this far,” as the agent testified.

At the family’s home, investigators also found a note Colt had apparently written, stating, “It’s not your fault,” and asking his family for forgiveness. He concluded by writing, “It’s out of my control.”