NASHVILLE, TENN. -- WARNING: This story 鈥� and the video at the top of this article - contain graphic details some may find disturbing.

The shooter who killed three students and three staff members at a Christian school in Nashville legally bought seven weapons in recent years and hid the guns from their parents before carrying out the attack by firing indiscriminately at victims and spraying gunfire through doors and windows, police said Tuesday.

The violence Monday at The Covenant School was the latest school shooting to roil the nation and was planned carefully. The shooter had drawn a detailed map of the school, including potential entry points, and conducted surveillance of the building before carrying out the massacre, authorities said.

The suspect, Audrey Hale, 28, was a former student at the school. Hale did not target specific victims -- among them three 9-year-olds and the head of the school -- but did target "this school, this church building," police spokesperson Don Aaron said at a news conference Tuesday.

Hale was under a doctor's care for an undisclosed emotional disorder and was not known to police before the attack, Metropolitan Nashville Police Chief John Drake said at the news conference.

If police had been told that Hale was suicidal or homicidal, "then we would have tried to get those weapons," Drake said. "But as it stands, we had absolutely no idea who this person was or if (Hale) even existed."

Tennessee does not currently have a "red flag" law, which lets police step in and take firearms away from people who threaten to kill.

On Tuesday night, Tennessee's governor said one of the victims, 61-year-old substitute teacher Cynthia Peak, was a close friend of his wife, Maria, and that the two had been scheduled to have dinner after Peak taught that day.

"Maria woke up this morning without one of her best friends," Gov. Bill Lee said, adding that his wife once taught with Peak and another victim, Katherine Koonce, and the women and "have been family friends for decades."

Hale legally bought seven firearms from five local gun stores, Drake said. Three of them were used in Monday's shooting. Police spokesperson Brooke Reese said Hale bought the guns between October 2020 and June 2022.

Hale's parents believed their child had sold one gun and did not own any others, Drake said, adding that Hale "had been hiding several weapons within the house."

Hale's motive is unknown, Drake said. In an interview with NBC News on Monday, Drake said investigators don't know what drove Hale but believe the shooter had "some resentment for having to go to that school."

Drake, at Tuesday's news conference, described "several different writings by Hale" that mention other locations and The Covenant School.

Asked at a Senate hearing whether the Justice Department would open an investigation into whether the shooting was a hate crime targeting Christians, U.S. Attorney General Merrick Garland said federal officials were working with local police to identify a motive.

Police have released videos of the shooting, including edited surveillance footage that shows the shooter's car driving up to the school, glass doors being shot out and the shooter ducking through one of them.

Additional video, from Officer Rex Engelbert's bodycam, shows a woman meeting police outside as they arrive and telling them that all the children were locked down, "but we have two kids that we don't know where they are."

The woman then directs officers to Fellowship Hall and says people inside had just heard gunshots. Three officers, including Engelbert, search rooms one by one, holding rifles and announcing themselves as police.

The video shows officers climbing stairs to the second floor and entering a lobby area, followed by a barrage of gunfire and an officer yelling twice: "Get your hands away from the gun." Then the shooter is shown motionless on the floor.

Police identified Engelbert, a four-year member of the force, and Michael Collazo, a nine-year member, as the officers who fatally shot Hale. The White House said President Joe Biden spoke Tuesday with Drake, Engelbert and Callazo to thank them for their bravery.

Police response times to school shootings have come under greater scrutiny after the attack in Uvalde, Texas, in which 70 minutes passed before law enforcement stormed the classroom. In Nashville, police said about eight minutes passed from the initial call to when officers arrived at the scene.

Surveillance video shows a time stamp of just before 10:11 a.m., when the attacker shot out the doors. Police said they got the call about a shooter at 10:13. Aaron said in an email Tuesday that dispatch records show officers arrived on campus shortly before 10:22.

At about 10:24, officers engaged the suspect, the chief said during the news conference. Within two minutes of that, the suspect was down, according to the dispatch records.

"There were police cars that had been hit by gunfire. As officers were approaching the building, there was gunfire going off," Drake said.

"We feel, our response right now, from what I've seen, I don't have a particular problem with it. But we always want to get better. We always want to get there in two or three minutes," he said, adding that traffic was "locked down" at the time.

Traffic was indeed stopped along a nearby two-lane road with a turning lane as police tried to weave their way to the school.

Police have given unclear information on Hale's gender. For hours Monday, police identified the shooter as a woman. Later in the day, the police chief said Hale was transgender. After the news conference, Aaron declined to elaborate on how Hale identified.

In an email Tuesday, police spokesperson Kristin Mumford said Hale "was assigned female at birth. Hale did use male pronouns on a social media profile." Later Tuesday, at the news conference, Drake referred to Hale with female pronouns.

Authorities identified the dead children as Evelyn Dieckhaus, Hallie Scruggs and William Kinney. The adults were Cynthia Peak, 61, Katherine Koonce, 60, and Mike Hill, 61.

The website of The Covenant School, a Presbyterian school founded in 2001, lists a Katherine Koonce as the head of the school. Her LinkedIn profile says she has led the school since July 2016. Peak was a substitute teacher, and Hill was a custodian, according to investigators.

Koonce was remembered as someone who would run toward 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."

Founded as a ministry of Covenant Presbyterian Church, the school is in the affluent Green Hills neighbourhood just south of downtown Nashville. It has about 200 students from preschool through sixth grade and roughly 50 staff members.

Before Monday's violence in Nashville, there had been seven mass killings at K-12 schools since 2006 in which four or more people were killed within a 24-hour period, according to a database maintained by The Associated Press and USA Today in partnership with Northeastern University. In all of them, the shooters were males.

The database does not include school shootings in which fewer than four people were killed, which have become far more common in recent years. Last week alone, for example, school shootings happened in Denver and the Dallas area within two days of each other.

------

Contributing to this report were Associated Press writers Denise Lavoie in Richmond, Virginia, John Raby in Charleston, West Virginia, and Stefanie Dazio in Los Angeles.