Colin Gray, the father of alleged Georgia school shooter Colt Gray, entered a not guilty plea Thursday morning to charges – including two counts of second-degree murder – alleging that he shares responsibility for the September shooting.

Gray did not appear in court, and the plea was entered on his behalf by his attorney, Jimmy Berry, who waived a formal arraignment.

Gray faces 29 charges, including two counts of second-degree murder and two counts of involuntary manslaughter. In the indictment, a grand jury said Gray gave his son “access to a firearm and ammunition after receiving sufficient warning that Colt Gray would endanger the bodily safety of another,” calling it “a substantial and unjustifiable risk.”

Colin Gray is only the third person charged in the US in connection with a school shooting by their child. Jennifer and James Crumbley were found guilty of involuntary manslaughter for allowing their son Ethan Crumbley to have a gun despite his declining mental health.

Ethan was convicted of killing four classmates at Oxford High School in Michigan and sentenced to life in prison without parole last year.

Investigators previously testified in court that Colin Gray bought the AR-15-style rifle allegedly used in the school shooting for Colt Gray as a Christmas present last year, only seven months after the family was questioned by law enforcement over online threats “to commit a school shooting.”

Colt Gray, 14, is charged with killing two students and two teachers at Apalachee High School in Winder, northeast of Atlanta, leaving nine others injured. He was indicted on 55 counts, including four counts each of malice murder and felony murder.

Colt Gray will be tried as an adult. He entered a not guilty plea last month and also waived arraignment.

Attorneys for the prosecution and defense declined to comment after Thursday’s brief court hearing. The judge did not set a date for the next hearing, but defense attorney Berry said they plan to file more than two dozen new motions in the case in the next two weeks.

Colin and Colt Gray have both been jailed since their arrests. Berry did not enter a request for bond Thursday.

Earlier this month, prosecutors issued subpoenas to three local shooting ranges for information about the Grays’ use of their facilities. Amazon also received a subpoena for information about their purchase history.

The Barrow County Sheriff’s Office said two of their deputies working as school resource officers rushed to the scene of the shooting, but were blocked by a haze of dust and smoke.

Their speed, along with the activation of a new schoolwide incident alerting system, is credited with preventing more deaths.

“Whether or not we die is a coin flip,” Deputy Chase Boyd told the Barrow News-Journal last month, “but our job is to stop the shooter from taking more lives.”

The fast response of Boyd and fellow deputy Brandon King stood in contrast to the deadly elementary school shooting in Uvalde, Texas, in 2022, when more than 300 officers responded to the scene but waited over an hour to confront the shooter.

There have been at least 76 school shootings in the United States so far this year, as of November 11. Twenty-four were on college campuses, and 52 were on K-12 school grounds. The incidents left 36 people dead and at least 103 other victims injured, according to CNN’s analysis of events reported by the Gun Violence Archive, Education Week and Everytown for Gun Safety.

This story has been updated with additional information.

CNN’s Dakin Andone and Lauren del Valle contributed to this report.