WINDER, Ga. (AP) — A shooter caused an unknown number of injuries at a high school outside of Atlanta on Wednesday morning, sending students scrambling for shelter in the football stadium as officers swarmed the campus and parents raced to find out if their children were safe.

A suspect was in custody, authorities said.

“What you see behind us is an evil thing,” Barrow County Sheriff Jud Smith said at a brief news conference outside Apalachee High School. He declined to give details about casualties, or about the suspect.

Jacob King, a sophomore football player, said he had dozed off in his world history class after a morning practice when he heard about 10 gunshots.

King said he didn’t believe the shooting was real until he heard an officer yelling at someone to put down their gun. King said when his class was led out, he saw officers shielding what appeared to be an injured student.

Ashley Enoh was at home Wednesday morning when she got a text from her brother, who’s a senior at Apalachee High School:

“Just so you know, I love you,” he texted her.

When she asked in the family group chat what was going on, he said there was a shooter at the school. Enoh’s younger sister, a junior at the school, said she had heard about the shooter and that everything was on lockdown.

Few details were immediately available from authorities, who were dispatched shortly before 10:30 a.m. to respond to an “active shooting,” the sheriff’s office said in a statement.

“Casualties have been reported, however details on the number or their conditions is not available at this time,” the statement added.

Helicopter video from WSB-TV showed dozens of law enforcement and emergency vehicles surrounding the school in Barrow County, about 50 miles (80 kilometers) northeast of Atlanta.

When Erin Clark, 42, received a text from her son Ethan, a senior at the high school, that there was an active shooter, she rushed from her job at the Amazon warehouse to the school. The two texted “I love you,” and Clark said she prayed for her son as she drove to the high school.

With the main road blocked to the school, Clark parked and ran with other parents. Parents were then directed to the football field. Amid the chaos, Clark found Ethan sitting on the bleachers.

Clark said her son was writing an essay in class when he first heard the gunshots. Her son then worked with his classmates to barricade the door and hide.

“I’m so proud of him for doing that,” she said. “He was so brave.”

Students had only started the school year a little over a month ago before the shooting Wednesday.

“It makes me scared to send him back,” she said. “I don’t know what I’m going to do.”

Traffic going to the school was backed up for more than a mile as parents tried to get to their children there.

“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,” Georgia Gov. Brian Kemp said in a statement.

“We will continue to work with local, state, and federal partners as we gather information and further respond to this situation,” Kemp added.

In a statement, the FBI’s Atlanta office said: “FBI Atlanta is aware of the current situation at Apalachee High School in Barrow County. Our agents are on scene coordinating with and supporting local law enforcement.”

The White House said President Joe Biden has been briefed by his Homeland Security Advisor, Liz Sherwood-Randall, about the shooting and the administration will coordinate with federal, state and local officials as it receives more information.

Apalachee High School has about 1,900 students, according to records from Georgia education officials. It became Barrow County’s second largest public high school when it opened in 2000, according to the Barrow County School System. It’s named after the Apalachee River on the southern edge of Barrow County.

The shooting had reverberations in Atlanta, where patrols of schools in that city were beefed up, authorities said. More patrols of Atlanta schools would be done “for the rest of the day out of an abundance of caution,” Atlanta Mayor Andre Dickens said.