Hours after a report of an active shooter caused mass hysteria at one Georgia high school Wednesday, students returned to their classrooms, authorities were calling the ordeal a hoax and a 16-year-old girl thought to be behind it all is in custody.

The incident happened at Jackson County Comprehensive High School.

The teen, whose identity has not been released, was charged with disrupting a public school, falsely reporting a crime, unlawful conduct during a 911 call and putting out a false public alarm, Jackson County Sheriff Janis Mangum said.

She has since been released to her parents, Channel 2 Action News reported.

The girl will be charged as a juvenile.

“All schools have been cleared, and law enforcement is investigating what has been definitively identified as a hoax call,” Jackson County Schools said in a Facebook post.

Before authorities gave the all-clear, there was chaos.

It started just before 8 a.m. when the teenage girl called Jackson County 911 and described an active shooter situation near the high school. That call prompted an evacuation and lockdowns at all county schools.

“Please understand that part of our protocol is anytime there is a possible incident at one school, all of our schools go on lockdown,” the district said in another Facebook post.

Parents flooded the high school to pick up their children, according to Channel 2.

Law enforcement agencies from across Jackson County and the GBI responded.

Jefferson police Chief Joe Wirthman said officers immediately started searching the school.

“If we saw people in the hallway,” Wirthman said, “we told them to get out.”

About 9 a.m., after authorities swept the school and the surrounding area and found no gunman and no signs of gunfire, officials allowed students to return to class. About 1,000 students attend the high school, the district said.

“All the kids are safe,” Mangum told The Atlanta Journal-Constitution.

In other news:

Nearly two dozen shell casings marked the ground at the scene in southeast Atlanta.