A Georgia teenager will spend the rest of his life in prison for killing four people and injuring nine others in a 2024 school shooting, a judge in the US has ruled.Colt Gray, 16, who last week pleaded guilty to 55 counts, including murder and assault charges, appeared impassive as a judge in Barrow County Superior Court delivered his sentence on Tuesday, local time."Your crimes do reflect permanent incorrigibility," Judge Nicholas Primm said. "You do not seem to be tormented by what you did. You seem to relish following in the footsteps of the murderers you idolise," he added.Judge Primm had two sentencing options: life with or without the possibility of parole.Colt Gray, a 14-year-old ninth-grader at the time of the September 4, 2024, shooting, brought an assault-style rifle he had received as a Christmas present from his father into Apalachee High School in Winder, Georgia, hidden inside a roll of poster board.Colt Gray pleaded guilty to 55 counts, including murder. (AP: Jason Getz/Atlanta Journal-Constitution/Pool)His father, Colin Gray, was convicted in March on 27 charges, including second-degree murder, for giving his son the rifle despite what prosecutors said were clear red flags, including a shrine to school shooters in the boy's room. ⁠It was a rare prosecution of a parent in connection with a child's mass shooting in the United States. Colin Gray is expected to be sentenced on Thursday.Colt Gray was charged as an adult for the shooting, in which he killed students Christian Angulo and Mason Schermerhorn, both 14, and teachers Cristina Irimie, 53, and Richard Aspinwall, 39.In hearings on Monday and Tuesday, prosecutors argued that Colt Gray was still driven by a desire to achieve the notoriety of other school shooters he admired. They played recordings of jailhouse calls weeks after the shooting in which Colt Gray asked his mother to tell him how the Internet's "true crime community" was reacting to his rampage.During one such call, Colt Gray laughed and said he was "in the big leagues … and not in a bad way.""The shooting was not the culmination of the plan — [it] was just one of the steps," said Barrow County District Attorney Brad Smith in his closing argument on Tuesday. "The plan was ultimate and lifelong fame."Mr Smith dismissed the defence's efforts to show that Colt Gray could be rehabilitated and safely rejoin society one day, comparing the teenager to a shark with inescapably violent instincts.His defence lawyer, Charlton Allen, sought to show that Colt Gray's traumatic and unstable childhood pushed him to embrace an online community that idolised violent crime. Mr Allen presented testimony from figures in Colt Gray's life, including his grandmother, that his parents abused drugs and neglected his basic needs.Colt Gray's shooting was his way of "reflecting the behaviours of the community that seems to be willing to accept him when his own parents won't," Mr Allen said in his closing argument.Reuters