The 28-year-old who shot dead six people at an elementary school in Nashville bought and concealed multiple weapons in the family home, despite evidence of mental health issues, police said Tuesday.
Two nine-year-old girls, a nine-year-old boy, two teachers and a school custodian died in the Monday attack, which instantly revived the bitter public debate over gun rights in the United States.
Nashville police chief John Drake told reporters that Audrey Hale, 28, had been receiving treatment for an "emotional disorder," and that the shooter's parents believed their child -- who lived at home with them -- had bought and later resold a single gun.
But Hale, who was killed during the attack, was heavily armed with two assault rifles and a handgun upon entering the Covenant School, a small Christian academy for about 200 students that the shooter attended as a pupil.
The shooter, identified by police as a female who had used male pronouns on social media, had prepared detailed maps of the school and also left a written manifesto that suggested attacks at other locations were planned.
"Audrey bought seven firearms from five different local gun stores here legally," Drake said.
"She was under doctors' care for an emotional disorder... Her parents felt that she should not own weapons."
"As it turned out, she had been hiding several weapons within the house," he continued.
Drake added that pupils and staff were not targeted individually and there was no known motive despite the manifesto being found.
- Video of police response -
In chilling security camera video, Hale is seen shooting through glass doors to enter the school before stalking the empty halls as emergency alarm lights flash.
Hale, wearing a black military-style vest, camouflage pants and red baseball cap, moved through the building, opening fire on children and staff.
Officers were on the scene within about 15 minutes of the first emergency call.
Bodycam footage showed police making their way through classrooms filled with small desks and paper craftwork.
Multiple gunshots are heard as officers close in on a sun-filled atrium upstairs, where the assailant was shot dead.
A former schoolmate, Averianna Patton, told CNN of a message that Hale sent on Instagram the morning of the shooting.
"One day this will make more sense," Hale wrote. "I've left behind more than enough evidence behind. But something bad is about to happen."
Patton said she called police to alert them at about the time the attack started.
In the search for a motive, Drake told NBC News that "there's some belief that there was some resentment for having to go to that school."
One of the young children killed was Hallie Scruggs, the daughter of the church's pastor, Chad Scruggs.
"We are heartbroken. She was such a gift," Chad Scruggs said in a statement to local media.
- Gun rights -
Asked whether Hale's gender identity may have been a factor, police said they were investigating all leads.
As the country digested another mass shooting, mourners left flowers and stuffed toys at a growing makeshift memorial outside the school. Some kneeled in prayer.
Chad Baker, 44, said he felt "horrified and very sad."
"I carry a gun with me most days, but I don't need an assault rifle," he told AFP.
"I don't think it should be as easy to buy flowers as it is a gun."
There were more than 24 million AR-15 style assault weapons in circulation in the United States by mid-2022, according to the NSSF firearm trade association.
President Joe Biden warned that gun violence was "ripping the soul of this nation," as he urged Congress to reinstate the national assault rifle ban, which existed from 1994 to 2004.
Efforts to ban the powerful weapons have run up against opposition from Republicans, staunch defenders of the constitutional right to bear arms.
The deadlock in Washington has come despite uproar over the recurrence of school massacres, including last year when a shooter in Uvalde, Texas, killed 19 students and two teachers.
Last year also marked 10 years since 26 people, including 20 children, were killed at Sandy Hook elementary school in Connecticut -- deeply shocking the nation, yet failing to produce meaningful progress on gun control.
Without that progress, many schools have turned to security measures such as metal detectors and active shooter drills instead.
"It's not on schools to figure out more security and revamp their protocol," said Nina Dyson, a mother of four attending a small demonstration in Nashville Tuesday seeking more regulation of firearms.
"There are parents all over the country demanding change for decades, and there (has) been none," the 35-year-old said at the protest, which had been planned before Monday's attack took place. - AFP