(ABC News) — The father of the 14-year-old student accused of opening fire at Apalachee High School in Winder, Georgia, has been arrested and charged with murder in connection with the deadly shooting, the Georgia Bureau of Investigation announced Thursday.

Colin Gray, 54, was charged with four counts of involuntary manslaughter, two counts of second-degree murder and eight counts of cruelty to children, the GBI said.

His son has also been charged with four counts of felony murder, with additional charges expected, the GBI said.

Two teachers and two students were killed in Wednesday morning’s shooting: math teacher and football coach Richard Aspinwall, 39; math teacher Christina Irimie, 53; and students Mason Schermerhorn, 14, and Christian Angulo, 14, officials said.

Eight students and one teacher were injured, officials said. All of the injured victims are expected to recover, Barrow County Sheriff Jud Smith said.

The suspect, Colt Gray, surrendered at the scene to the school resource officers, the GBI said. He was taken into custody at 10:30 a.m. ET, seven minutes after the initial service call went out, according to the Barrow County Sheriff’s Office, which employs the school resource officers.

Colt Gray will be tried as an adult, the GBI said.

He is being held at the Gainesville Regional Youth Detention Center and will appear in court virtually on Friday morning, authorities said.

An AR-platform-style weapon was used in the shooting, according to GBI Director Chris Hosey.

Officials said they did not yet have answers for how Colt Gray was allegedly able to obtain the gun and get it into the school. Colt Gray was interviewed by investigators and the GBI, but Smith did not disclose further details.

Teachers at the high school had IDs that alert law enforcement during an active incident — a new safety system that was implemented just one week ago, the sheriff said.

A motive has not yet been determined and it is unknown if the victims were targeted, investigators said.

The suspect had an apparent affinity for mass shooters, multiple sources familiar with the investigation told ABC News. Investigators are scouring concerning social media posts from accounts associated with Colt Gray that mention prior mass shootings and those who carried them out, the sources said.

The GBI said in a statement Thursday, “This is day 2 of a very complex investigation & the integrity of the case is paramount. We ask for the public’s patience as we work to ensure a successful prosecution & justice for the victims.”

The autopsies will be performed on Thursday, the GBI said.

In May 2023, authorities interviewed the suspect, who was then 13, about alleged threats to commit a school shooting, according to the FBI.

The FBI said it received anonymous tips about online threats to commit a school shooting and the online threats contained photos of guns.

The boy’s dad told authorities he had hunting rifles in the house, saying, “Colt is allowed to use them when supervised but does not have unfettered access to them,” according to the police report obtained by ABC News.

When the 13-year-old was interviewed, he “assured me that he never made any threats to shoot up any school,” an officer wrote, according to the report.

The online threat included a user profile written in Russian, and investigators said at the time that the translation of the Russian letters spelled out the name Lanza, referring to Adam Lanza, who committed the Sandy Hook Elementary School mass shooting in 2012.

“I could not substantiate the tip I received from the FBI to take further action,” an officer wrote in his report. “At this time, due to the inconsistent nature of the information received by the FBI, the allegation that Colt or [his father] is the user behind the Discord account that made the threat cannot be substantiated.”

“At that time, there was no probable cause for arrest or to take any additional law enforcement action on the local, state, or federal levels,” the FBI said on Wednesday.

The sheriff’s office said it “alerted local schools for continued monitoring of the subject.”

Discord said in a statement that the account was created on April 2, 2023, and removed by the platform on May 21, 2023, “for violating our policy against extremism.”

“At that time, Discord’s Safety team immediately responded to law enforcement, provided all requested information to aid in their investigation, and acted swiftly to remove the user from the platform,” Discord said. “Based on our ongoing investigation since then, we have no indication that the suspect used Discord to discuss or plan this horrific attack.”