Nashville school shooter Audrey Hale, a 28-year-old transgender artist and former student, legally purchased the firearms used in the attack behind the family's back despite serious emotional issues that required a doctor's attention, according to authorities.

Metro Nashville Police Chief John Drake also told reporters Tuesday that a motive in the Monday attack at the Covenant School remains unknown and that the shooter had targeted the school but not any individual victims specifically. The school operates as a ministry of Nashville's Covenant Presbyterian Church.

"We've interviewed the parents of Audrey Hale, and we've determined that Audrey bought seven firearms from five different local gun stores here legally," Drake said during a news briefing. "They were legally purchased. Three of those weapons were used yesterday during the horrific tragedy."

Hale's parents told police they were only aware of one firearm, which they believed Hale had previously sold, he said.

NASHVILLE SCHOOL SHOOTING: AUDREY HALE POLICE BODYCAMS RELEASED

Audrey Hale photo

Audrey Hale was identified by police as the gunman who opened fire at the Covenant School on Monday morning, killing six people. (Fox News)

"They were under the impression that when she sold the weapon, she did not own any more," he said. "As it turned out, she was hiding several weapons inside the house."

He said the shooter was under a doctor's care for an unspecified emotional disorder but was previously unknown to law enforcement

"Her parents felt she should not own weapons," he said. But Hale had secretly build a collection.

WATCH: Metro Nashville Police Chief John Drake's full news briefing

In addition to the three guns recovered at the scene, police took a sawed-off shotgun and another shotgun from the family home. It was not immediately clear what the remaining two guns were.

NASHVILLE SCHOOL SHOOTER AUDREY HALE: WHO IS 28-YEAR-OLD TRANSGENDER FORMER STUDENT WHO OPENED FIRE AT SCHOOL

Hale killed six people Monday, three 9-year-old students, including the pastor's daughter, and three adults.

Hale drove to the school on Monday around 10:15 a.m. in a Honda Fit, where police found writings that indicated her attack was "calculated and planned," police said.

Police also recovered diagrams of the school layout, with possible entry points highlighted, as well as drawing depicting Hale in the same outfit worn during the attack, Drake said.

NASHVILLE SCHOOL SHOOTING: OFFICERS WHO TOOK OUT COVENANT SHOOTER IDENTIFIED

Audrey Hale portrait inset over surveillance video

Covenant School shooter Audrey Hale, 28, pictured in a driver's license photo and on school surveillance video released by Nashville police. Hale killed three 9-year-olds and three adults Monday morning at a private school linked to a church. (Metro Nashville Police Department)

Within 15 minutes, responding officers took down the shooter, who was killed at the scene following an exchange of gunfire.

Police said Hale opened fire on responding officers from a second-story window before a team inside the building, including Officers Rex Engelbert and Michael Collazo, put an end to the carnage.

The victims were found spread out around the building and were not located in a common area, Drake told reporters.

The first victim, 61-year-old custodian Michael Hill, was found dead near the entrance where Hale shot through a glass door to get inside, he said. According to a GoFundMe for his family, Hill was a father of eight.

Photo collage of the three victims at the Nashville shooting.

Three of the six Covenant School victims, from left, Mike Hill, 61, Katherine Koonce, 60, and Hallie Scruggs, 9, were killed in the Nashville school shooting, Monday, March 27, 2023. (Fox News)

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Head of School Katherine Koonce, 60, was found in a hallway near the office, he said.

The school is part of the Covenant Presbyterian Church, and victims included the pastor's daughter, Hallie Scruggs, as well as Evelyn Dieckhaus and William Kinney, all 9. Cynthia Peak, 61, a substitute teacher, was also killed.

Police said Hale had attended the Covenant School at some point in the past. Records show the shooter went on to graduate high school eight years ago and graduated from the Nossi College of Art last year.