Colin Gray, 55, gave his son Colt the AR-15-style rifle used in the shooting as a Christmas present in 2023 despite warnings that the boy had threatened to carry out a school shooting.Colt Gray, who is now 16, pleaded guilty to the September 2024 attack at Apalachee High School in the Georgia town of Winder and was sentenced on Tuesday to life in prison without the possibility of parole.Colin Gray, his father, was convicted by a jury in March of second-degree murder, involuntary manslaughter and other offenses in connection with the shooting carried out by his son, which left two 14-year-old students and two teachers dead and nine people wounded."It is clear you failed as a parent," Superior Court Judge Nicholas Primm told Gray at his sentencing hearing. "You did not provide a stable household. You didn't have him in school."None of those failures helped your case," Primm said. "But those aren't why you were convicted. You were convicted because the warning lights were flashing brighter and brighter and you didn't get him help and you didn't remove his access to the guns."School shootings are a shockingly regular occurrence in the United States, where guns outnumber people and regulations on purchasing even powerful military-style rifles are lax.