Police received a call of a teacher being shot around 14:00 local time (19:00 GMT) on Friday at Richneck Elementary School. When they entered the classroom, they found a six-year-old student restrained by a school employee.

Chief Drew said the child fired one round at his teacher. He added that the “shooting was not accidental, it was intentional”, and that it took place while Ms Zwerner was giving a lesson.

Ms Zwerner was struck through her hand and into her upper chest, Chief Drew said. She then made sure her students were safely outside the classroom, before making her way down to the school’s administration office to call for help, he said.

“She turned around to make sure that every one of those students was safe,” Chief Drew said.

As the building was placed under lockdown, a woman who was picking up her grandchildren saw Ms Zwerner appear in the doorway of the school’s front office.

Lowanda Sample-Rusk told the New York Times: “She said, ‘Call 911, I’ve been shot.’ And then she fainted.”

Another parent told the Washington Post that the shooting occurred after the teacher tried to confiscate the weapon from the child.

Police said they found a 9mm Taurus pistol in the class near the student’s desk, along with his backpack, a mobile phone and one spent shell casing.

Chief Drew said police determined through an interview with the child’s mother that the gun was bought legally and stored in their home.

The child, who has not been identified, was taken into custody and is undergoing evaluation in hospital, police said, adding that they will seek a temporary detention order.

Police are continuing to investigate the incident, Chief Drew said, including conducting more interviews with witnesses and local child services.

Officials said that while the school – which has about 550 pupils – had metal detectors, pupils were checked at random and not every child was inspected.

A pupil at the school – Novah Jones, who is in fifth grade and was in a different classroom – described the moment her class was locked down.

“I was scare,” she told CNN. “It was like my first lockdown and I didn’t know what to do, so I just hid under my desk like everybody was.”

One parent, Steve Gonzalez, whose child was in the classroom at the time, said Ms Zwerner’s actions were selfless.

After being struck by the bullet, “she screamed at her kids to run away”, he told Fox News.

Shortly after the shooting, students were evacuated to the school’s gym before they were reunited with their families. Chief Drew described tearful parents waiting to see their children.

One unnamed British mother picking up her child told local media that guns were “biggest problem in this country”.

“Why is it so bad?” she continued.

The school will remain closed all week to give students and families “time to heal,” the chief said.