The Nashville school principal ran towards the gunfire as a former student tried to mow down her child pupils.
Covenant School Principal Dr Katherine Koonce, 60, was left for dead in one of the facility's corridor - which pointed to her having a "confrontation" with the shooter.
Audrey Hale, a transgender man who used he/him pronouns and called himself Aiden, blasted his way through a locked glass door at the entrance of the building at around 10.13am Monday.
The alarm was immediately raised as Hale prowled the corridors, choosing his victims at random.
In chilling CCTV footage from inside the school, he was seen wandering the halls with his assault rifle.
Former FBI agent and Nashville City Council member Russ Pulley confirmed that Koonce had put her own life at risk to save the youngsters.
"It is my understanding from a witness at the school, that Katherine Koonce was on a Zoom call when she heard the first shot," said Pulley.
"She immediately ended the call, got up, and headed straight for the shooter.
"She did what principals and headmasters do; she protected her children.
"In addition, she prepared the school by seeking advanced level active shooter training and from witnesses at the scene, this protocol, details of which I cannot provide, saved countless lives."
"The headmaster, Dr Koonce, upon hearing the first shots, ran toward the danger," he wrote on Facebook.
"She also made sure the school was prepared with active shooter training and protocols. Those actions saved countless lives."
Chief of Nashville Police John Drake said he had no doubt the principal moved towards the danger rather than hiding from it, though he stopped short of providing further details.
"There was a confrontation, I'm sure – you can tell the way she was lying in the hallway," Drake said.
Hale is said to have had a well-planned and targeted attack in mind as they drove to the school on Monday morning, armed with multiple weapons, to take lives.
Hale, 28, shot their way into The Covenant School in Nashville, Tennessee before killing the school’s top administrator, a substitute teacher, a custodian, and three 9-year-olds.
But their background and motives behind the horrific crime remain unclear as more details emerge from the authorities' investigation.
Authorities described Hale as a "lone zealot", who had written a manifesto ahead of the attack which police are analysing, along with some writings, to understand the shooter's motives.
Police Chief John Drake did not disclose what drove the shooter to carry out the attack, but he mentioned that the shooter had conducted surveillance of the school and had drawn a detailed map of it, including potential entry points.
