Two students and two teachers were killed in a shooting at Apalachee High School in Winder, Georgia, on Wednesday morning, according to the Georgia Bureau of Investigation.
Another nine victims were taken to hospitals with injuries, the GBI said.
The suspect -- 14-year-old Colt Gray, a student at Apalachee High School -- was encountered by officers within minutes, and he immediately surrendered and was taken into custody, the GBI said. He will be charged with murder and he will be tried as an adult, the GBI said.
It's not clear if any of the victims were targeted, authorities said.
Senior Sergio Caldera, 17, said he was in chemistry class when he heard gunshots.
"My teacher goes and opens the door to see what's going on. Another teacher comes running in and tells her to close the door because there's an active shooter," Caldera told ABC News.
He said his teacher locked the door and the students ran to the back of the room. Caldera said they heard screams from outside as they "huddled up."
At some point, Caldera said someone pounded on his classroom door and shouted "open up!" multiple times. When the knocking stopped, Caldera said he heard more gunshots and screams.
He said his class later evacuated to the football field.
Kyson Stancion said he was in class when he heard gunshots and "heard police scream, telling somebody, 'There's a shooting going on, get down, get back in the classroom.'"
"I was scared because I've never been in a school shooting," he told ABC News.
"Everybody was crying. My teacher tried to keep everybody safe," he added.
Dad Jonathan Mills said he experienced an "emotional roller coaster" as he and his wife rushed to the school and waited to get ahold of their son, Jayden.
It was "exhilarating" and "overwhelming" to reach Jayden, a junior, and learn he was OK, Mills told ABC News.
Mills, a police officer, said, "Growing up in this area, you don’t expect things like that to happen."
"I have three children. All three of them go to this cluster of schools, and you never think about that," he said.
Winder is about 45 miles outside of Atlanta.
Barrow County Schools will be closed through the end of the week, the superintendent said.
Barrow County Sheriff Jud Smith called the shooting "pure evil."
President Joe Biden and Vice President Kamala Harris were briefed on the shooting, according to the White House.
"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," Biden said in a statement. "Students across the country are learning how to duck and cover instead of how to read and write. We cannot continue to accept this as normal."
The president highlighted his work to combat gun violence, including signing the Bipartisan Safer Communities Act into law and launching the first White House Office of Gun Violence Prevention. But he stressed that more must be done.
"After decades of inaction, Republicans in Congress must finally say 'enough is enough' and work with Democrats to pass common-sense gun safety legislation," Biden said. "We must ban assault weapons and high-capacity magazines once again, require safe storage of firearms, enact universal background checks, and end immunity for gun manufacturers. These measures will not bring those who were tragically killed today back, but it will help prevent more tragic gun violence from ripping more families apart."
Harris said at a campaign event in New Hampshire, "Our hearts are with all the students, the teachers and their families."
"This is just a senseless tragedy on top of so many senseless tragedies," she said. "We have to end this epidemic of gun violence."
"This is one of the many issues that's at stake in this election," Harris said.
"Let us finally pass an assault weapons ban and universal background checks and red flag laws," she said. "It is a false choice to say you are either in favor of the Second Amendment, or you want to take everyone's guns away. I am in favor of the Second Amendment, and I know we need reasonable gun safety laws in our country."
Georgia Gov. Brian Kemp said he is "heartbroken."
"This is a day every parent dreads, and Georgians everywhere will hug their children tighter this evening because of this painful event," he said in a statement. "We continue to work closely with local, state, and federal partners to make any and all resources available to help this community on this incredibly difficult day and in the days to come."
In Atlanta, authorities will "bolster patrols" around schools on Wednesday "out of an abundance of caution," Atlanta Mayor Andre Dickens said in a statement.
"My prayers are with the high school students, staff and families affected by the senseless act of violence," Dickens said.
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