The 14-year-old suspect was a student at the school and is in custody.
A Georgia community is in mourning after two students and two teachers were killed in a shooting at Apalachee High School on Wednesday morning, according to authorities.
Another nine victims were taken to hospitals with injuries, but are all expected to survive, according to the Georgia Bureau of Investigation Director Chris Hosey.
The suspect, a 14-year-old student, is in custody and will be tried as an adult, the GBI said.
Hosey identified the four victims Wednesday evening, whose ages ranged from 14 to 53 years old. Here's what we know about the victims.
Mason Schermerhorn was a 14-year-old student at the high school, according to the GBI.
Christian Angulo was a 14-year-old student at the high school, according to the GBI.
Richard Aspinwall was a 39-year-old teacher at Apalachee High School, according to the GBI. He was a math teacher who also coached football as the defensive coordinator, according to the school's website.
Christina Irimie was a 53-year-old math teacher at Apalachee High School, according to the GBI.
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."
MORE | 'I had so much fear': Students recount shooting at Georgia high school
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."
Among the victims, Northeast Georgia Health System said three people with non-life-threatening gunshot wounds were taken to its hospitals. Five people with symptoms related to anxiety and panic attacks also came to its hospitals, it said.
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."
Attorney General Merrick Garland said, "I'm devastated for the families who have been affected by this terrible tragedy. The Justice Department stands ready to provide any resources or support."
Georgia Gov. Brian Kemp added that 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."
Kemp canceled a planned speech in front of the Republican Jewish Coalition in Las Vegas Wednesday night to fly back to Georgia in the wake of the shooting, a source confirmed to ABC News.
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.
So far in 2024 there have been 385 mass shootings as of September 4, including this latest one in Georgia, according to the ABC News data team.
This is Georgia's 16th mass shooting so far this year.
This time last year there were 485 mass shootings.
The Gun Violence Archive, which defines a mass shooting as one with four or more people injured or killed - not including the perpetrator - counted 656 Mass Shootings in 2023, 646 in 2022, 689 in 2021 and 610 in 2020.
ABC News' Josh Margolin, Brandon Baur, Faith Abubey and Miles Cohen contributed to this report.