The Nashville school shooter had planned the massacre for months in advanced and studied other mass murderers before killing six people, police have revealed.

Audrey Hale, 28, had plotted her sick attack months before she killed three kids and three adults at The Covenant School last week.

Cops also revealed on Monday that she fired 152 rounds from two assault rifles and a handgun during the vile shooting that rocked the US.

Update: Nashville school shooter, Audrey Hale fired 152 rounds from an assault rifle and handgun and studied other mass murderers before killing six including�three�kids

Officials haven’t released a motive for the slaying of victims, Hallie Scruggs, William Kinney, Evelyn Dieckhaus, all 9, and headmistress Dr. Katherine Koonce, 60, substitute teacher Cynthia Peak, 61, and chef Mike Hill, 61.

State Governor Bill Lee also addressed the state on Monday April 3, and proposed having an armed guard stationed at every school in the state.

A statement from Metropolitan Nashville Police department said: ‘The ongoing investigation into the March 27 murders of six persons inside The Covenant School continues to show, from all information currently available, that killer Audrey Hale acted totally alone

‘In the collective writings by Hale found in her vehicle in the school parking lot, and others later found in the bedroom of her home, she documented, in journals, her planning over a period of months to commit mass murder at The Covenant School.

‘The writings remain under careful review by the MNPD and the FBI’s Behavioral Analysis Unit based in Quantico, Virginia.

‘The motive for Hale’s actions has not been established and remains under investigation by the Homicide Unit in consultation with the FBI’s Behavioral Analysis Unit.

‘It is known that Hale considered the actions of other mass murderers.

‘The investigation shows that Hale fired a total of 152 rounds (126 5.56 rifle rounds and 26 nine millimeter rounds) from the time she shot her way into the school until she was killed by police.

‘Two officers fired on Hale. Officer Rex Engelbert discharged a total of four 5.56 rounds from his rifle; Officer Michael Collazo discharged a total of four rounds from his department-issued nine millimeter pistol.

‘Scores of police personnel from a number of components responded to the Covenant call last Monday.

‘The department’s Professional Wellness Section is conducting critical incident debriefings, including daily wellness checks, for involved personnel.

‘The MNPD’s Homicide Unit is leading the investigation into the murders of the six victims. The Cold Case Unit is working with the TBI in the investigation of the fatal police shooting of Hale.’

To prevent a school mass shooting from occurring again in the state, Tennessee Governor Lee announced a proposal on Monday to have an armed guard present at every school in the state.

‘There was no excuse to no have a guard at every school,’ Lee said.

He estimated the budget to employ and train guards would cost $140 million.

The governor also revealed other plans to dedicate $8 million toward mental health services in schools.

Hale, who was transgender born female, used the names Audrey and Aiden but her preferred pronouns were he/him according to a LinkedIn page.

Police confirmed on Tuesday that she had previously attended the school in Nashville, Tennessee, but her motive for the shooting was unclear.

Police Chief John Drake added that Hale had been suffering from an ’emotional disorder’ at the time of the shooting.

Hale has been described as having ‘high-functioning’ autism, but police revealed she also was under doctors’ care.

Her parents, Norma and Ronald Hale – knew that she had a weapon at one time, but told her to sell it because they thought she couldn’t be trusted with it.

Instead, she hid her stockpile and added to it, buying seven different weapons in total from five local stores.

Chief Drake added: ‘Law enforcement knew nothing about the treatment, and it is apparent that she should not own weapons’

Authorities also confirmed that Hale’s mother, Norma, had asked her what was in a red backpack she was carrying on the morning of the murders but she dismissed her question.

Before bursting into the school, the killer sent a haunting final message to Averianna Patton on Instagram. The two played basketball together in middle school.

At 9.57am, 16 minutes before cops were first notified to the shooting, Audrey wrote: ‘So basically that post I made on here about you, that was basically a suicide note.

‘I’m planning to die today. THIS IS NOT A JOKE!!! You’ll probably hear about me on the news after I die.

‘This is my last goodbye. I love you. ‘See you again in another life.’
‘Audrey (Aiden)’.

Patton immediately called the cops to report the messages but it was already too late.