NASHVILLE (AP) — Six people were killed at a small, private Christian school just south of downtown Nashville on Monday after a shooter opened fire inside the building of about 200 students, police said.

Police received a call about an active shooter at The Covenant School — a Presbyterian school — around 10:15 a.m. Authorities said that about 15 minutes after that call to police, the shooter was dead. The remaining students were ferried to a safe location to be reunited with their parents.

Here's what we know and don't know about the shooting:

HOW MANY PEOPLE WERE KILLED?

Nashville police said six people, including three students, were killed. The victims were identified as Cynthia Peak, 61; Katherine Koonce, 60; Mike Hill, 61; and Evelyn Dieckhaus, Hallie Scruggs, and William Kinney, all age 9. Police officers also killed the shooter.

The website of The Covenant 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.

On Tuesday night, Tennessee Gov. Bill Lee said Peak was a close friend of his wife, Maria, and that the two had been scheduled to have dinner after Peak taught that day.

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WHAT DO WE KNOW ABOUT THE NASHVILLE SHOOTER?

Police gave unclear information on the shooter's gender. For hours, police identified the shooter as a 28-year-old woman and eventually as Audrey Hale. Then at a late afternoon press conference, the police chief said that Hale was transgender. After the news conference, police spokesperson Don 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."

Police said Hale was a former student of the school, but it was unclear if Hale had any current affiliation with the school or was related to anyone in the school at the time of the shooting. Police said the shooter had made a detailed map of the school and conducted surveillance of the building before carrying out the massacre.

Police said Hale had two "assault-style" weapons and a pistol when Hale shot through the front door to enter the building. Police said Tuesday that Hale had legally purchased seven firearms from five different stores in the Nashville area.

Investigators found a sawed-off shotgun, a second shotgun and other unspecified evidence during a search of Hale's home. Police Chief John Drake said Hale's parents were unaware that Hale had obtained most of the weapons. They told police Hale was under a doctor's care for an undisclosed emotional disorder, Drake said. Hale's parents also said they believed Hale had only purchased one gun and had sold it.

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HOW WAS THE NASHVILLE SHOOTER KILLED?

A team of five Nashville police officers entered the school after the initial call, said Aaron, the police spokesperson. While clearing the first floor of students and staff, they heard shots being fired on the second floor.

Two of the officers opened fire in response and fatally struck Hale at about 10:27 a.m., police said. Police identified Rex Engelbert, a four-year member of the force, and Michael Collazo, a nine-year member, as the officers who fatally shot Hale.

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WHAT VIDEOS HAVE BEEN RELEASED AND WHAT DO THEY SHOW?

Police released body camera footage Tuesday from two officers that showed a team of Nashville Police SWAT officers briefly speaking to a staff member outside before entering the building and searching several classrooms quickly. They then rush toward the second floor where gunshots could be heard.

Officers are heard yelling commands, followed by a barrage of gunfire. Shortly after, an officer yells for Hale to stop moving and "get your hands away from the gun." Hale, whose face and injuries are blurred in the released footage, is seen laying on the floor motionless.

The six-minute video supplements a release late Monday, of about two minutes of 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.

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DO WE KNOW THE MOTIVE?

Investigators were sent to the shooter's home shortly after Hale was killed, police said. Hale had a map of the school with a planned route for the shooting, and officers found writings, police said.

No motive has been confirmed by police, but officials said Hale targeted the school, not any particular individual killed in the shooting.

Chief Drake said officers found writings that detailed the plan to attack the school and potentially other locations. He said in an interview with NBC News that investigators believe the shooter had "some resentment for having to go to that school."

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HOW MANY SCHOOL SHOOTINGS HAVE THERE BEEN SINCE COLUMBINE?

There have been 15 mass shootings at schools or universities in the U.S. since the Columbine High School massacre in 1999. Mass shootings are defined as more than four people dying, not including the perpetrator, according to a database compiled by The Associated Press, USA Today and Northeastern University, in addition to other AP reporting:

Of those 15 shootings, 175 people have died, the data shows.