Hale identified as transgender and was “under a doctor’s care for an emotional disorder”, John Drake, Nashville’s police chief, said.

Hale had left behind a “manifesto” and other documents, indicating the rampage had been meticulously planned.

The victims appeared to have been chosen at random.

They were nine-year-old Evelyn Dieckhaus, Hallie Scruggs and William Kinney; Katherine Koonce (60), the school’s head teacher; Cynthia Peak (61), a substitute teacher; and Mike Hill (61), a custodian.

Hallie’s father Chad is a pastor at the Covenant Presbyterian Church, which is connected to the school.

In a statement given to ABC News, he said his family were heartbroken.

“Through tears we trust that she is in the arms of Jesus who will raise her to life once again,” the statement read.

The school in a statement said: “Our community is heartbroken. We are grieving tremendous loss and are in shock coming out of the terror that shattered our school and church.”

Ms Koonce was remembered as someone who would run towards danger, not away from it. “I guarantee you if there were kids missing [during the shooting], Katherine was looking for them,” friend Jackie Bailey said. “And that’s probably how she got in the way – just trying to do something for somebody else. She would give up her own life in order to save somebody else’s.”

Hale had legally bought seven firearms from five different gun shops in the area and hid the guns from family members before the attack, police revealed.

Mr Drake said police “knew nothing” about Hale’s medical supervision, but said “her parents felt that she should not own weapons”.

Mr Drake said Hale’s parents had told police they were under the impression the attacker did not own any weapons, having previously sold one gun. “As it turned out, she had been hiding several weapons in the house,” he added.

The police chief said detectives were still working to identify a motive for the deadly attack. He said they were probing whether the ­shooter’s transgender identity was a factor and said Hale, a former student at the Covenant School, had “some resentment for having to go to that school”.

Mr Drake used female pronouns to refer to the shooter but officials have indicated Hale was identifying as male and went by the name of Aiden.

It was unclear when Hale attended the Presbyterian school, for children aged between four and 12.

The school is affiliated with the evangelical Presbyterian Church in America, which has spoken of the “sinfulness” of transgender and homosexual desire and conduct, according to The New York Times.

Residents in the neighbourhood in south-west Nashville where Hale grew up said they were still reeling from the tragedy yesterday.

One neighbour, who did not want to be named, said: “She [Hale] was very shy and kept to herself,” the neighbour said. “I did not think she was capable of doing anything like this.”

The resident said he was shocked to hear there were guns in the Hale family home.

“From what I understand, the mother would not have let that be,” he said, adding that she appeared to keep a sharp eye on Hale.

Residents described the neighbourhood as close-knit, with some families, including Hale’s, living on the street for over 35 years. Many are members of Covenant church, to which the school is attached.

It has emerged Hale had messaged a friend minutes before the massacre, saying “one day this will make more sense” because they had “left more than enough evidence behind”.