NASHVILLE - A 28-year-old woman heavily armed with several guns opened fire on Monday at a private Christian school she once attended in Tennessee’s capital city, killing three children and three adult school employees before police killed her, authorities said.

There was no immediate official word on a possible motive for the violence, which unfolded on a warm spring morning not long after classes began at The Convenant School, whose students consist mostly of elementary school-age children.

The woman was carrying at least two semi-automatic rifles and a handgun, police said.

The suspect had drawn detailed maps of the school, including entry points for the building, and left behind a “manifesto” and other writings that investigators were examining, Police Chief John Drake told a news briefing.

Mr Drake identified the suspect as a woman by the name of Audrey Elizabeth Hale, 28, a resident of the Nashville area and referred to the assailant by female pronouns. But in response to reporters’ questions, the chief said: “She does identify as transgender.”

Whether the suspect identified as a man or woman was not made clear.

Later, the Tennessean newspaper quoted a police spokesman as saying Hale used he/him pronouns. Hale used male pronouns on a LinkedIn page that listed recent jobs in graphic design and grocery delivery.

Mr Drake said police were working on a theory about what may have precipitated the shooting and would “put that out as soon as we can”. He said the suspect had no known prior criminal history.

In a subsequent NBC News television interview, Mr Drake said investigators believed the shooting stemmed from “some resentment” the suspect harboured “for having to go to that school” as a younger person.

The police chief did not specify the nature of such presumed resentment, or whether it had anything to do with the suspect’s gender identity or the Christian orientation of the school. Mr Drake said the school was singled out for attack, but the individual victims were targeted at random.

The Metropolitan Nashville Police Department began receiving calls at 10.13am about a shooter at the school, and arriving officers reported hearing gunfire coming from the building’s second floor, police spokesman Don Aaron told reporters.

Two officers from a five-member team shot the assailant in a lobby area, and she was pronounced dead soon after.

“The police department response was swift,” Mr Aaron said.

The attacker gained entry to the school by firing through one of the doors, the police chief said.

Three students were pronounced dead after they were taken to Monroe Carell Jr Children’s Hospital at Vanderbilt with gunshot wounds, John Howser, a hospital spokesman, said in a statement. Three adult staff members were also killed by the shooter, police said.

The victims were identified as Evelyn Dieckhaus, Hallie Scruggs, and William Kinney, all aged 9, along with staffers Mike Hill, 61, a school custodian, Cynthia Peak, 61, a substitute teacher, and Katherine Koonce, 60, listed on the Covenant website as “head of school”.

Besides the dead, no one else was shot, Mr Aaron said.

Deadly mass shootings have become commonplace in the United States in recent years, but a female attacker is highly unusual. Only four of 191 mass shootings catalogued since 1966 by The Violence Project, a non-profit research centre, were carried out by a female attacker.

Reacting to the shooting in Washington, US President Joe Biden urged Congress again to pass more gun reform legislation.

“It’s sick,” he said, addressing the issue during an event at the White House. “We have to do more to protect our schools, so they aren’t turned into prisons ... I call on Congress again to pass my assault weapons ban.

“We have to do more to stop gun violence. It’s ripping our communities apart, ripping the soul of this nation.”

US Senator Marsha Blackburn, a Tennessee Republican, said on Twitter that her office stands “ready to assist” those affected by the shooting.

But Rosanne Cash, daughter of Nashville country music icon Johnny Cash and a singer-songwriter in her own right, responded by criticising Ms Blackburn’s ties to the National Rifle Association (NRA) gun lobby.

“You vote against every common sense gun control bill that comes across your desk, you’ve taken over US$1 million (S$1.3 million) from the NRA and you rank 14th in all Congress for NRA contributions. Spare us the hand-wringing,” she tweeted.

At the state level, in 2021 Tennessee did away with its permit requirement for carrying a concealed handgun and now allows anyone aged 21 and older to carry a firearm, either openly or concealed, without a permit, as long as they are legally allowed to purchase the weapon.

Possessing a handgun is outlawed in Tennessee for anybody who has been convicted of a serious offence involving violence or drugs.

Parents were told to gather at the nearby Woodmont Baptist Church to be reunited with their children. One woman was visibly distraught as she was escorted alone out of the church to an awaiting squad car by police officers.

The Covenant School, founded in 2001, is a ministry of Covenant Presbyterian Church in the Green Hills neighbourhood of Nashville with about 200 students, according to the school’s website. The school serves preschool through sixth graders and held an active shooter training programme in 2022, WTVF-TV reported.

Nashville Mayor John Cooper expressed sympathy for the victims and wrote on social media that his city “joined the dreaded, long list of communities to experience a school shooting”.

There have been 89 school shootings – defined as anytime a gun is discharged on school property – in the US so far in 2023, according to the K-12 School Shooting Database, a website founded by researcher David Riedman. In 2022, there were 303 such incidents, the highest of any year in the database, which goes back to 1970. REUTERS