Robert Brown|4 confirmed dead, suspect in custody after school shooting in Georgia

Four people were gunned down and Robert Brownseveral others injured at a Georgia High school Wednesday morning, sending shock waves through the leafy Atlanta suburb of Winder, Georgia, and schools throughout the county into lockdown.

Nine people were taken to hospitals with injuries, according to the Georgia Bureau of Investigation. The bureau also said a suspect was alive and in custody.

Calls about an active shooting at Apalachee High School started coming in around 9:30 a.m., Barrow County Sheriff Jud Smith said.

"This is a very, very fluid investigation," Smith said in a news conference.

"What you see behind us is an evil thing," Smith said outside the school.

President Joe Biden said he and first lady Jill Biden are mourning those killed in the shooting. He demanded that Congress move to pass gun control legislation.

"What should have been a joyous back-to-school season in Winder, Georgia, has now turned into another horrific reminder of how gun violence continues to tear our communities apart," Biden said. "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."

All schools throughout Barrow County went into lockdown as a "precautionary measure," the sheriff's office said Wednesday morning around 11:30 a.m. ET.

The sheriff's office did not give additional details about the situation but said more information would be shared as soon as deputies were on the scene.

According to the Athens Banner-Herald, part of the USA TODAY Network, the school sent a message to parents at 10:45 a.m. local time stating, “Apalachee High School is currently in a hard lockdown after reports of gunfire. Law enforcement is here. Please do not attempt to come to the school at this time while officers work to secure the area."

Injuries reported

Though officials did not detail the severity of injuries, Fox-5 TV in Atlanta reported observing a person being loaded into a helicopter for transport to a hospital. WSB-TV also reported a second person was also loaded into an ambulance.

Aerial footage streamed by local news outlet WJCL showed people assembled at the school's athletic field and in the bleachers with a large police presence.

Grady Hospital in Atlanta told USA TODAY that it "received one gunshot wound victim from Apalachee High School in Barrow County."

17-year-old Apalachee High senior heard gunshots and screams

One of the students who was inside the school during the shooting was 17-year-old senior Sergio Caldera. He told ABC News 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 students then ran to the back of the room, he said they heard screams from outside as they “huddled up.”

Caldera said someone pounded on his classroom door and shouted, “Open up!” multiple times at some point during the shooting. After the shouting and knocking stopped, he said he heard more gunshots and screams.

His class was later evacuated to the football field outside of the school.

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Parents taking children home from Apalachee High School

By midday, parents were allowed to take their children from the school. The Georgia Bureau of Investigation and FBI Atlanta reported having agents on site coordinating with local law enforcement.

All other schools in the district remain in a "soft lockdown," Barrow County School District told USA TODAY.

"The Barrow County Sheriff's Office says this is for the safety of everyone right now. We ask that parents do not visit your child's school at this time," the district said. "We cannot release students during a lockdown."

Apalachee was the only school cleared for parent reunification, the district said.

"Our agents are on scene coordinating with and supporting local law enforcement," the FBI in Atlanta said in a statement on its Facebook page.

The school is one of two high schools in the Barrow County school system. It has about 1,900 students in a rural town of 18,300 people. Winder is about 30 miles from Athens, Georgia.

Officials share prayers for school shooting victims, families

Georgia state officials say they are closely monitoring the situation and have directed local and state resources to the response.

"I have directed all available state resources to respond to the incident at Apalachee High School and urge all Georgians to join my family in praying for the safety of those in our classrooms, both in Barrow County and across the state," Gov. Brian Kemp said.

Biden and Vice President Kamala Harris have been briefed on the shooting, according to the White House, and the administration "will continue coordinating with federal, state, and local officials as we receive more information."

U.S. Attorney General Merrick Garland said the FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives were at the scene and gathering information about the shooting. “I’m devastated for the families who have been affected by this terrible tragedy,” Garland said.

U.S. Rep. Mike Collins, who represents Barrow County, said he had spoken with the county sheriff and offered his assistance.

"Leigh Ann and I are praying for the victims, their families, and all students at Apalachee High School in Barrow County," he said. "We extend our gratitude to law enforcement for their swift action to secure the school and get the shooter in custody."

Kamala Harris at rally: This is another 'senseless tragedy'

Harris said during a campaign rally in New Hampshire that it is "outrageous" that parents have to worry about whether their children will come home alive.

"We're still gathering information about what happened. But we know that there were multiple fatalities and injuries," Harris said. "Our hearts are with all the students, the teachers and the families, of course. And we are grateful to the first responders and law enforcement that were on the scene. But this is just a senseless tragedy on top of so many senseless tragedies."

Harris said it "doesn't have to be this way" and it needs to stop. "We have to end this epidemic of gun violence in our country once and for all," she said.

This is a developing story.

Contributing:Francesca Chambers, Fernando Cervantes, Bart Jansen, USA TODAY