Several people were injured in a shooting at Apalachee High School in Winder, Georgia, Wednesday morning, according to Barrow County Sheriff Jud Smith.

A suspect is in custody, the sheriff’s office said.

More precise information on the number of victims and their condition was not immediately clear, the sheriff’s office said.

Sergio Caldera, a 17-year-old high school graduate, said he was in chemistry class when he heard gunshots.

“My teacher goes to the door and opens it to see what’s going on. Another teacher comes running and tells her to close the door because someone is shooting,” Caldera told ABC News.

He said his teacher locked the door and the students ran to the back of the classroom. Caldera said they heard screams coming from outside as they “crouched down.”

At one point, Caldera said, someone banged on his classroom door and shouted “Open up!” several times. When the banging stopped, he heard more gunshots and screams, Caldera said.

He said his class was later evacuated to the soccer field.

The Barrow County School District announced that Apalachee High School was “cleared for classroom closure” and all other schools in Barrow County were under a “soft lockdown.”

“The Barrow County Sheriff’s Office says this is for everyone’s safety at this time. Please do not attend your child’s school at this time. We are unable to dismiss students during a curfew,” the school district said in a statement. “We will let you know as soon as the Barrow County Sheriff’s Office says dismissal is possible.”

Winder is located about 45 miles outside of Atlanta.

President Joe Biden has been briefed on the shooting. “His administration will continue to work with federal, state and local authorities as we receive more information,” the White House said.

Agents from the FBI and Georgia Bureau of Investigation are on site.

Attorney General Merrick Garland said: “I am devastated for the families affected by this terrible tragedy. The Department of Justice stands ready to provide all resources and support.”

Georgia Governor Brian Kemp said he was “praying for the safety of people in our classrooms, both in Barrow County and across the state.”

In Atlanta, authorities will increase 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 violence in Winder,” Dickens said.

This is a developing story, please check back later for updates.

ABC News’ Josh Margolin and Miles Cohen contributed to this report.