Three children and three adults were killed Monday in an active-shooter event at a Nashville, Tenn., elementary school, police said.

The mass shooting started around 10:15 a.m. Monday at The Covenant School, a Presbyterian elementary school for students in preschool through sixth grade in the Green Hills neighborhood.

The Metropolitan Nashville Police Department identified the victims: Evelyn Dieckhaus, 9, Hallie Scruggs, 9, William Kinney, 9, Cynthia Peak, 61, Katherine Koonce, 60, and Mike Hill, 61.

Nashville PD said its officers fatally wounded the shooter, a 28-year-old Nashville resident identified as Audrey Hale. The suspect was armed with at least two “assault-style” rifles and a handgun, police spokesman Don Aaron said. At least two of the weapons were believed to have been obtained legally in the Nashville area, according to the police Chief John Drake. Police said a search of Hale’s home turned up a sawed-off shotgun, a second shotgun and other unspecified evidence.

The suspect, Drake said, was "at one point a student at that school," based on his initial findings. Drake later said the suspect was transgender; after the news conference, Aaron declined to elaborate on how Hale most recently identified.

Drake said that officials "feel that she identifies as trans, but we’re still in the initial investigation into all of that and if it actually played a role into this incident."

The chief said that the attack was targeted; the suspect had drawn a detailed map of the school, including potential entry points, and done surveillance before the shooting.

“We have a manifesto. We have some writings that we’re going over that pertain to this date, the actual incident,” Drake said. “We have a map drawn out of how this was all going to take place.”

He later told NBC News that investigators believe the shooter had “some resentment for having to go to that school."

Late Monday night, police released approximately two minutes of edited surveillance video showing the shooter’s car driving up to the school from multiple angles, including one in which children can be seen playing on swings in the background. Next, an interior view shows glass doors to the school being shot out and the shooter ducking through one of the shattered doors.

More footage from inside shows the shooter walking through a school corridor holding a gun with a long barrel and walking into a room labeled “church  office,” then coming back out. In the final part of the footage, the shooter can be seen walking down another long corridor with the gun drawn. The shooter is not seen interacting with anyone else on the video, which has no sound.

When police arrived, they heard shooting on the second floor of the school, where they shot the suspect 14 minutes after receiving the first call, Aaron said. He described it as a “lobby-type area,” and not a classroom.

Officers began clearing the first story of the school when they heard gunshots coming from the second level, Aaron said.

A spokeswoman for Vanderbilt University Medical Center earlier confirmed to Spectrum News that three children were pronounced dead on arrival with gunshot wounds at Monroe Carell Jr. Children’s Hospital at Vanderbilt. Aaron announced the deaths of the three adults shortly after.

One police officer suffered a hand injury from broken glass, authorities said. Aaron said he was not aware of any other shooting victims.

He said there were no police officers present or assigned to the school at the time of the shooting because it is a church-run school.

Students walked to safety Monday, holding hands as they left their school surrounded by police cars, to a nearby church to be reunited with their parents.

On a typical day, the school has a little more than 200 students inside and 40 to 50 faculty and staff members, Aaron said.

Jozen Reodica heard the police sirens and fire trucks blaring from outside her office building nearby. As her building was placed under lockdown, she took out her phone and recorded the chaos.

“I thought I would just see this on TV,” she said. “And right now, it’s real.”

Rachel Dibble, who was at the church as families reunited in the nearby church, described the scene as everyone being in “complete shock.”

“People were involuntarily trembling,” said Dibble, whose children attend a different private school in Nashville. “The children … started their morning in their cute little uniforms they probably had some Froot Loops and now their whole lives changed today.”

At an event on Monday, President Joe Biden called the shooting “heartbreaking, a family’s worst nightmare.”

“We have to do more to stop gun violence,” he said during an event at the White House. “It's ripping our communities apart, ripping at the very soul of the nation. And we have to do more to protect our schools so they aren't turned into prisons.”

Biden reiterated his call for Congress to pass a ban on semi-automatic weapons.

First lady Jill Biden, speaking to reporters at the National League of Cities summit in Washington, said: “I am truly without words. Our children deserve better. We stand with Nashville in prayer.”

The killings come as communities around the nation are reeling from a spate of school violence, including the massacre at an elementary school in Uvalde, Texas, last year; a first grader who shot his teacher in Virginia; and a shooting last week in Denver that wounded two administrators.

Monday's shooting was the 129th mass shooting so far this year, according to the Gun Violence Archive.

“In a tragic morning, Nashville joined the dreaded, long list of communities to experience a school shooting,” Mayor John Cooper wrote on Twitter. “My heart goes out to the families of the victims. Our entire city stands with you.”

Tennessee Gov. Bill Lee said in a tweet that he is "closely monitoring the tragic situation at Covenant.

"As we continue to respond, please join us in praying for the school, congregation & Nashville community," he wrote.

Sen. Marsha Blackburn, R-Tenn., tweeted that she and her husband "are heartbroken to hear about the shooting at Covenant School in Nashville." She added that her office is in contact with federal, state and local official and "we stand ready to assist."