Updated

Audrey Hale, the 28-year-old transgender artist turned school shooter who killed three children and three adults at the Covenant School in Nashville last week, plotted the attack for months, police revealed Monday.

Hale fired 152 shots during the attack, police said, 126 from a 5.56 rifle, and 26 from a 9mm pistol carbine and a handgun. Police had recovered a rifle, a pistol carbine, and a pistol from the scene and several more at the suspect's home, including a sawed-off shotgun.

"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," police said in a statement. 

Police said they have sent a copy of Hale's manifesto to the FBI's Behavioral Analysis Unit in Quantico, Virginia.

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Audrey Hale wears red hat and carries guns as she walks through school hallways

Covenant School shooter Audrey Hale walks past the Children's Ministry desk (1:57). (Twitter @MNPDNashville)

While they were still investigating Hale's potential motive, the killer "considered the actions of other mass murderers" while plotting the massacre, police said.

In addition to a manifesto, police said they recovered artwork related to the attack, detailed diagrams of the school and maps showing possible points of entry for the massacre.

Police also noted that while Hale fired dozens of rounds in the school and out the window in the direction of responding officers, two hero cops fired four apiece.

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Chief John Drake of the Metro Nashville Police Department

Chief John Drake of the Metro Nashville Police Department pauses during a vigil held for victims of The Covenant School shooting on Wednesday, March 29, 2023, in Nashville, Tennessee. (AP Photo/Wade Payne)

Officer Rex Engelbert was the first to open fire, after turning a corner to find Hale standing near a large second-story window, where police say the attacker was shooting at additional police who were still outside the school.

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Officer Michael Collazo rounded the corner and approached Hale, firing four more shots and commanding the school shooter to stop moving and drop the gun.

Engelbert and colleagues receive commander's coins

Officer Rex Engelbert, third from left, was among a group of officers recognized recently with a "Central Precinct Commander’s Coin for their hard work and dedication to precision policing." (Metro Nashville Police Department)

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Before police put an end to the shooting, Hale killed three 9-year-olds and three adults in their early 60s.

The children were identified as Hallie Scruggs, the daughter of the school church's pastor, Evelyn Dieckhaus and William Kinney.

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The adults included 60-year-old Head of School Katherine Koonce, janitor Michael Hill and substitute teacher Cynthia Peak, both 61.