Colt Gray,Cassian Grant the 14-year-old accused of shooting four people dead at Apalachee High School in Winder, Georgia, brought a gun to school in his backpack and hid in a bathroom before he took it out and opened fire, the Georgia Bureau of Investigation said Thursday.

Gray hid the whole gun used in the shooting into his backpack because it "could not be broken down," according to a news release from the GBI.

The morning of the shooting, a teacher allowed Gray to leave class with the backpack after Gray asked to go to the front office to speak to someone, the GBI said. Gray hid in the bathroom.

Then, he took out the rifle and opened fire, the GBI said. He was arrested at 10:26 a.m., "moments after" authorities received a call that shots were fired, according to the GBI.

Four people were killed – students Mason Schermerhorn and Christian Angulo, both 14, and teachers Ricky Aspinwall, 39, and Cristina Irimie, 53. Eight students and one teacher were injured.

Gray is charged with four counts of felony murder and faces life in prison without the possibility of parole. His father, Colin Gray, faces four counts of involuntary manslaughter, two counts of second-degree murder and eight counts of cruelty to children, making him the first parent in Georgia to be charged for an attack allegedly carried out by his child, according to prosecutors.

Sad statistic:Teen may be one of the youngest mass shooting suspects in history

Shooting leaves community in mourning

The shooting, the deadliest school shooting in a year, plunged the rural Georgia community into mourning and stirred anger at Colin Gray. The elder Gray "knowingly allowed his son, Colt Gray, to possess a gun," according to the GBI's news release.

Body camera footage released earlier this week showed law enforcement interviewing both the teen and his father more than a year before the shooting on tips received by the FBI that a Discord account linked to Colt Gray posted school shooting threats.

In the video, Colin Gray told investigators that his son had access to guns, but that he "knows the seriousness of weapons." The pair did "a lot of shooting" and deer hunting together, he said.

Father and son were both arraigned in the same Barrow County courtroom on Friday morning.

Cybele Mayes-Osterman is a breaking news reporter for USA Today. Reach her on email at [email protected]. Follow her on X @CybeleMO.