A 14-year-old student suspected of opening fire at a Georgia high school and killed four people had previously been investigated by the FBI over threats to commit a school shooting.
Two students and two teachers at Apalachee High School in Winder, about an hour's drive from Atlanta, were shot dead as chaos broke out on the school campus.
The victims were named as Mason Schermerhorn and Christian Angulo, both 14, and teachers Richard Aspinwall and Christina Irimie.
The suspect, named as Colt Gray, 14, was arrested on campus and will be prosecuted as an adult.
At least nine other people — eight students and one teacher — were taken to hospitals with injuries following Wednesday’s attack. All were expected to survive, Barrow County Sheriff Jud Smith said.
The teenage suspect had been interviewed after the FBI received anonymous tips in May 2023 about online threats to commit an unspecified school shooting, the agency revealed following the attack.
The sheriff's office interviewed the then-13-year-old and his father, who said there were hunting guns in the house but the teen did not have unsupervised access to them. The boy also denied making any online threats.
"At the time, there was no probable cause for an arrest or to take any additional law enforcement action on the local, state or federal levels," the FBI added in a statement.
Students were left scrambling for shelter in their classrooms and a football stadium as officers swarmed the school and parents raced to find out if their children were safe.
Some barricaded doors with desks and chairs as the words “hard lockdown” appeared on a screen in their classroom and the lights began flashing.
Sophomore Kaylee Abner was in geometry class when she heard the gunshots. She and her classmates were forced to hide behind their teacher's desk.
The student later entered the school’s football stadium where she saw teachers who had taken off their shirts to help treat gunshot wounds.
Two school resource officers encountered the shooter within minutes after a report of shots fired went out, authorities said.
The suspect, a student at the school, immediately surrendered and was taken into custody.
He is being charged as an adult with murder. Authorities said the weapon was an assault-style rifle.
The state Division of Family and Children's Services also had previous contact with the suspect and will investigate whether that has any connection with the shooting.
Authorities were still looking into how the suspect obtained the gun used in the shooting and got it into the school in Barrow County.
At an afternoon news conference, Mr Smith choked up as he began to speak. He said he was born and raised in the community and his kids are in the school system.
"My heart hurts for these kids. My heart hurts for our community," he said. "But I want to make it very clear that hate will not prevail in this county. I want that to be very clear and known. Love will prevail over what happened today."
It was the latest among dozens of school shootings across the US in recent years.
The classroom killings have set off fervent debates about gun control and frayed the nerves of parents whose children are growing up accustomed to active shooter drills in classrooms. But they have done little to move the needle on national gun laws.
Before Wednesday, there had been 29 mass killings in the US so far this year and at least 127 people had died in the incidents.
There were 217 deaths from 42 mass killings last year, making 2023 one of the deadliest years on record for school shootings in America.
"It's just outrageous that every day, in our country, in the United States of America, that parents have to send their children to school worried about whether or not their child will come home alive," Vice President Kamala Harris said during a campaign stop in New Hampshire.
In a message posted to social media, former President Donald Trump said: "These cherished children were taken from us far too soon by a sick and deranged monster."
