A 14-year-old has been charged with murder after four people were killed and at least nine injured in a school shooting in the US state of Georgia, according to local authorities.
Students scrambled for shelter at the school's football stadium as officers swarmed the campus and parents raced to find out if their children were safe.
The Georgia Bureau of Investigation (GBI) said the shooting happened at a high school outside of Atlanta.
In a press conference hours after the shooting, the GBI said Colt Gray, a student from the school, was in custody as the suspect and will be charged and tried as an adult.
Gray was confronted by a deputy in the school and immediately got on the ground and surrendered, the county sheriff said.
The 14-year-old had been interviewed by local law enforcement last year for making online threats about a school shooting, after an investigation by the Federal Bureau of Investigation.
The FBI said in a statement a 13-year-old and his father had been interviewed in 2023. It did not identify the teen, but Georgia officials said the statement was in connection to the subject in custody.
"The father stated he had hunting guns in the house, but the subject did not have unsupervised access to them.
"The subject denied making the threats online. Jackson County alerted local schools for continued monitoring of the subject," the FBI said, adding that there was no probable cause to make an arrest.
Two of the four people killed on Wednesday were students, and the other two were teachers, authorities confirmed.
They said the gunman was armed with an "AR platform-style weapon", or semiautomatic rifle.
"What you see behind us is an evil thing," Barrow County Sheriff Jud Smith said at a brief news conference outside Apalachee High School.
The incident, which took place at the school about 80 kilometres north-east of Atlanta, appeared to be under control and students were being released at midday, a Barrow County Schools spokesperson said.
Local TV stations broadcast images of parents lining up in cars on a road outside the school, hoping to be reunited with their children.
The school, which had an enrolment of nearly 1,900 last year, began classes on August 1.
Sheriff Smith said the first call law enforcement received about a shooting at the school came at about 9:30 am, local time, which would have been just over an hour after classes had started for the day.
'I love you'
When Erin Clark, 42, received a text from her son Ethan, a senior at the high school, that there was an active shooter, she rushed from her job at the Amazon warehouse to the school.
The two texted "I love you," and Ms Clark said she prayed for her son as she drove to the high school.
With the main road blocked to the school, Ms Clark parked and ran with other parents to the football field, where she found her son sitting on the bleachers amid the chaos.
Sophomore Shantal Sanvee, who was in a classroom near the gunshots, said "I saw, like, a whole lot of blood. And it was just, it was just horrible."
"I don't think I want to be here for like a long time now," she added.
As an officer led the students towards the football stadium, freshman Michelle Moncada was in tears. People who she knew had been shot.
"I was just really, really nervous," she said.
The stadium was filled with tear-stricken students wondering whether their friends were okay. She saw one of her friends on the floor, grazed by a bullet.
"It doesn't feel real," Ms Moncada said.
Renewed calls for gun reform
The White House said in a statement that President Joe Biden had been briefed on the shooting "and his administration will continue coordinating with federal, state, and local officials as we receive more information".
"Jill and I are mourning the deaths of those whose lives were cut short due to more senseless gun violence and thinking of all of the survivors whose lives are forever changed," Mr Biden said in a statement, calling on Republicans to work with Democrats to pass "common-sense gun safety legislation".
Vice-President Kamala Harris, the Democratic Party nominee for president, called the shooting a "senseless tragedy".
"We've gotta stop it. We have to end this epidemic of gun violence," Ms Harris said at the start of a campaign event in New Hampshire.
Georgia's Governor Brian Kemp said in a statement: "This is a day every parent dreads, and Georgians everywhere will hug their children tighter this evening because of this painful event."
The shooting was the first "planned attack" at a school this fall, said David Riedman, who runs the K-12 School Shooting Database.
Apalachee students returned to school last month; many other students in the US are returning this week.
The US has seen hundreds of shootings inside schools and colleges in the past two decades, with the deadliest resulting in over 30 deaths at Virginia Tech in 2007.
The carnage has sparked pitched debate over gun laws and the US Constitution's Second Amendment, which enshrines the right "to keep and bear arms".
AP/Reuters
