Casualties were reported in an active shooter situation at Apalachee High School in Winder, Georgia, on Wednesday morning, according to the Barrow County Sheriff's Office.
One suspect is in custody, the sheriff's office said.
The incident is over and a local hospital is "treating multiple gunshot wounds," according to one source briefed on the situation.
Details on the number of victims and their conditions were not immediately clear, the sheriff's office 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.
Apalachee High School was "cleared for dismissal" and all other Barrow County Schools are on a "soft lockdown," the Barrow County School District said.
"The Barrow County Sheriff's Office says this is for the safety of everyone right now. Please do not visit your child's school at this time. We cannot release students during a lockdown," the school district said in a statement. "We will let you know as soon as BCSO says it is all clear for dismissal."
Winder is about 45 miles outside of Atlanta.
President Joe Biden has been briefed on the shooting. "His administration will continue coordinating with federal, state, and local officials as we receive more information," according to the White House.
Agents from the FBI and the Georgia Bureau of Investigation are at the scene.
Georgia Gov. Brian Kemp said he's "directed all available state resources to respond."
Kemp said he's "praying for the safety of those in our classrooms, both in Barrow County and across the state."
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. (1/2)
— Governor Brian P. Kemp (@GovKemp) September 4, 2024
This is a developing story. Please check back for updates.
ABC News' Josh Margolin and Miles Cohen contributed to this report.
