The 28-year-old, who is said to be a former student at Covenant Presbyterian Church School, was shot dead by police on an upper floor of the school.
Hale broke into the school by shooting through a side door before opening fire on students and staff with two assault-style rifles and a handgun.
Metro Nashville Police Chief John Drake said Hale was not believed to have any previous criminal record.
He said a “manifesto” and a map of the school grounds showing entrances had been found at the killer’s home.
Asked at a press conference whether there was anything found in a police search of Hale’s home that could have suggested a motive for such a horrific crime, Chief Drake said: “We have a manifesto, we have some writings we’re going over that pertain to this day, the actual incident.
“We have a map drawn out of how this was all going to take place.
“There’s right now a theory that we may be able to talk about later but it’s not confirmed, and so we’ll put that out as soon as we can.”
A sawed-off shotgun, a second shotgun, and other evidence was also found at Hale’s home, police said.
Police have identified the suspected shooter by their name at birth; Hale reportedly was a transgender man who used he/him pronouns, though law enforcement officials initially described the suspect as a woman in the aftermath of the shooting. Police did not provide another name but on the suspect’s social media accounts they refer to themselves as Aiden.
In answer to a question as to whether Hale’s transgender status might have any bearing on a motive, Chief Drake said: “There is some theory to that. We’re investigating all the leads and once we know exactly, we will let you know.”
He said that the attack was targeted and that had been considering targeting another location – which was not identified – but apparently decided not to because of the level of security around it.
“Right now we believe it was a lone assailant, and we don’t anticipate any further damage at this time,” said the police chief.
He added in an interview with NBC News that investigators believe the killer had “some resentment for having to go to that school”.
A LinkedIn account suggests Hale was an illustrator and graphic designer based in Nashville. The account says Hale was working for AH Illustrations and had previously been an illustrator at Nossi College of Art. It also mentions jobs with Grocery Shopper and as a cat sitter.
A neighbour, Sandy Durham, told the Daily Beast: “I do know Audrey, I’ve known her since she was a baby. I had just gotten out of the shower when all of this started happening. I didn’t really know anything more than that. Something was going on next door. It’s just tragic for everybody. The sweet children that were hurt, killed, the adults. All of it.”
Asked if there were any warning signs she said: “Never. She was very sweet. I don’t know what happened. It’s very scary.”
Another neighbour said he was shocked at Monday’s attack, describing Hale as a normal “quiet” person, from a family without any apparent interest in guns.
“If I had to imagine, Audrey’s parents are probably just as shocked as everybody in the neighborhood is…It just doesn’t seem real,” Sean Brashears told the outlet.
“There’s nothing that would have led me to believe that she was capable of such a thing or that she or anybody in that family would have access to, much less ever used, a gun. They just don’t seem like the family that, like, is around guns. They’re not talking about going to a gun range or they’re not going hunting.”
The police chief added that while there was no known history of mental illness, it was a lead that was being investigated.
However, a friend said that Hale had spoken about feeling suicidal in the past and messaged her on Instagram minutes before the shooting rampage.
Hale sent a series of direct messages to friend Averianna Patton via Instagram on Monday morning.
In the harrowing messages sent at 9.57am, Hale revealed plans to die by suicide telling Ms Patton “this is my last goodbye” and that she would soon be reading about it “on the news after I die”.
“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.”
Just 16 minutes later – at 10.13am – law enforcement received the first 911 call reporting shots fired inside The Covenant School.
Ms Patten told NewsChannel 5 that she contacted the Suicide Prevention Help Line at 10.08am to try to get her friend help.
“Audrey has shared with others that she had been suicidal in the past and I knew to take this serious,” Ms Patton said.
She then called the Nashville Davidson County Sheriff’s Office where she was directed to Nashville’s non-emergency number.
She later learned from the news and from friends what Hale had done.
“After phone calls from friends and Audrey’s name was released as the shooter at Covenant Nashville school, I learned that Audrey was the shooter and that she had reached out to me prior to the shooting,” Ms Patton said.
“My heart is with all of the families affected and I’m devastated by what has happened.”
Details about the killer came to light as the six victims were also identified.
Evelyn Dieckhaus, Hallie Scruggs and William Kinney, all aged 9, were fatally shot.
Katherine Koonce, age 60, and Cynthia Peak and Mike Hill, both age 61, were also among the six victims.
Koonce is listed on The Covenant School’s website as “head of school.”
Hill was a school custodian, and Peak was a substitute teacher, according to law enforcement officials speaking to reporters on 27 March.
If you are experiencing feelings of distress and isolation, or are struggling to cope, the Samaritans offers support; you can speak to someone for free over the phone, in confidence, on 116 123 (UK and ROI), email firstname.lastname@example.org, or visit the Samaritans website to find details of your nearest branch.
If you are based in the USA, and you or someone you know needs mental health assistance right now, call National Suicide Prevention Helpline on 1-800-273-TALK (8255). The Helpline is a free, confidential crisis hotline that is available to everyone 24 hours a day, seven days a week.
If you are in another country, you can go to www.befrienders.org to find a helpline near you.