The perpetrator of the shooting that killed six people at an elementary school in Nashville managed to buy weapons and hide them in her family home, despite evidence that she was suffering from mental disorders, police said.

Two girls, a boy, all nine years old, and three school staff were killed in Monday's attack, which revived the fierce debate over gun rights in the United States.

Many people, including parents with their children, came to a memorial in front of The Covent School in Nashville on Tuesday afternoon, many with tears in their eyes.

Lisbeth Melgar, who brought her two children with her to visit the monument, told AFP: "It is unimaginable that these wonderful boys will not return home."

Nashville Police Chief John Drake earlier announced that the 28-year-old shooter Audrey Hale was being treated for a "psychiatric disorder" and that Hill's parents believed their daughter who lived with them had bought one weapon and later sold it.

But Hayel, who was killed in the attack, was carrying two assault rifles and a pistol when she stormed the small school of about 200 students, where the attacker was a former schoolgirl.

Police referred to Hale as a female, while introducing herself on social media by male names, in possession of maps of the school, and left behind a statement suggesting further attacks were planned.

Active shooter Audrey Elizabeth Hale drove to Covenant Church/School in her Honda Fit this morning, parked, and shot her way into the building. She was armed with 2 assault-type guns and a 9 millimeter pistol. pic.twitter.com/mIk2pDmCwQ

— Metro Nashville PD (@MNPDNashville) March 28, 2023

Details of the massacre

"Audrey legally purchased 7 guns from 5 different local gun stores," Drake said. "She was receiving medical attention because of a mental disorder. Her parents think she shouldn't have had weapons," he said, adding: "It turns out she was hiding a lot of weapons inside the house."

Drake stressed that pupils and staff were not individually targeted and that the motives were unknown. In CCTV footage, Hayel is seen firing at doors to enter the school before bursting into empty halls as emergency lights turn on.

Wearing a black sleeveless jacket, spotted pants and a red baseball cap, she walked inside the building, shooting at children and staff.

The officers arrived about 15 minutes after the first emergency call.

Police are seen in the cameras mounted on their clothes moving through rows filled with small tables and paper art.

A former classmate, Averiana Button, told CNN that Hale posted a message on Instagram on the morning of the shooting, writing, "One day it will make sense," adding, "I left behind more than enough evidence, but something bad will happen."

Patton said she called police to alert them around the time the attack began.

Drake told NBC News that "there's a kind of resentment that she has to go to that school."

Asked if Hayel's gender was a factor that led to the attack, police said they were investigating all leads.