Nashville: At a private Christian school the suspect once attended in the state's capital city on Monday, a heavily armed 28-year-old fatally shot three children and three adult staff members before being shot and killed by police, according to authorities.

Although the motive was not immediately clear, Police Chief John Drake told reporters that the suspect had left behind a "manifesto" and other writings that investigators were looking through. He also had drawn detailed maps of the school, including the location of the building's entrances.

The Covenant School, where most of the students are of elementary school age, was the scene of the most recent incident in an epidemic of deadly mass gun violence that has regularly terrorised even the most beloved of US institutions.

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Drake identified the attacker as Audrey Elizabeth Hale, 28, a local of the Nashville area, and used the pronouns "she" and "her" to refer to the attacker. The chief stated without further explanation that the suspect identified as transgender.

Hale used he/him pronouns, according to a police spokesperson quoted in The Tennessean newspaper. On a LinkedIn page listing recent jobs in graphic design and grocery delivery, Hale used male pronouns.

The attacker can be seen on a school video that was later made public by the police shooting through glass doors and prowling the hallways while brandishing a semi-automatic rifle. In a video where only the shooter was visible, Hale was dressed in a black vest over a white T-shirt, camouflage pants, and a red baseball cap on the inside.

Drake stated at a news conference held in the early evening that police were developing a theory regarding what might have led to the shooting and would "put that out as soon as we can." He said the suspect had no known prior criminal history.

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Investigators, according to Drake, believe the shooting was motivated by "some resentment" the suspect had for having to attend that school when he was younger. Drake made this statement in a subsequent NBC News television interview.

The police chief didn't elaborate on the kind of presumptive resentment or whether it was related to the suspect's gender identity or the school's Christian ethos. Drake claimed that although the school was specifically targeted, the individual victims were picked at random.

Gunfire was heard coming from the second floor of the building when officers arrived, according to reports from police spokesperson Don Aaron. The Metropolitan Nashville Police Department started receiving calls about a shooter at the school at 10:13 a.m.

Two officers from a five-member team shot the assailant in a lobby area, and the suspect was pronounced dead by 10:27 a.m. Aaron remarked that the police department responded quickly. According to the police, the suspect was carrying two assault-style rifles and a 9 mm pistol.

Evelyn Dieckhaus, Hallie Scruggs, and William Kinney, all 9, were among the victims, as were 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."

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According to the school's website, the Covenant School, founded in 2001, is a ministry of Covenant Presbyterian Church in Nashville's Green Hills neighbourhood, with approximately 200 students. It serves preschool through sixth graders and will hold an active shooter training programme in 2022, according to WTVF-TV.