NASHVILLE — As a heartbroken Nashville community grapples with the mass shooting that claimed the lives of three 9-year-old children and three adults at a private Christian school, police are uncovering more details about the 28-year-old shooter.

The attack unfolded over 14 minutes Monday morning at The Covenant School, with the heavily armed shooter firing into the elementary school to gain access and killing six people before being fatally shot by responding police officers.

The parents of the shooter, identified as Audrey Hale, told police they knew Hale had bought and sold one weapon and believed that was the extent of it, Metro Nashville Police Chief John Drake said Tuesday.

Young children, the head of their school and its custodian. These are the victims of the Nashville school shooting

But Hale, who was under care for an emotional disorder, had legally bought seven firearms that were hidden at home, Drake said. Three of those weapons, including an AR-style rifle, were used in the attack Monday.

Police have said the attack was pre-planned, finding that Hale had detailed maps of the school as well as writings related to the shooting and had scouted a second possible attack location in Nashville. Hale’s childhood friend also revealed the shooter sent her disturbing messages just before the attack.

The attack marked the 19th shooting at a school or university so far in 2023 that left at least one person wounded, a CNN count shows. It was also the deadliest US school shooting in nearly a year, since the May attack in Uvalde, Texas, left 21 dead.

As terrified schoolchildren and teachers were led to safety out of The Covenant School Monday, word spread of those who were lost: three young children, the head of their school, its custodian and a substitute teacher.

“All of Tennessee was hurt yesterday, but some parents woke up without children, children woke up without parents and without teachers, and spouses woke up without their loved ones,” said Tennessee Gov. Bill Lee, who also lost a close family friend in the shooting.

The shooter sent a disturbing Instagram message to a childhood friend just before 10 a.m. Monday, saying “I’m planning to die today” and that it would be on the news, the friend Averianna Patton told CNN on Tuesday.

Patton, a Nashville radio host, told CNN she was the shooter’s childhood basketball teammate but they hadn’t spoken in years and is unsure why she received the message. Patton said she then called a suicide prevention line and the Nashville Davidson County Sheriff’s Office at around 10:13 a.m.

That’s the same time police in Nashville say they got a 911 call of an active shooter inside The Covenant School.

Writings left behind by Hale revealed the attack “was calculated and planned,” police said. The shooter had a drawing of how to enter the building and “assaults that would take place,” Drake said at a Tuesday news conference.

The attacker was “prepared for confrontation with law enforcement, prepared to do more harm than was actually done,” Drake said Monday.

Hale had targeted the school, but it is believed the students were fired upon at random, police said.

“This school, this church building was a target of the shooter, but we have no information at present to indicate that the shooter was specifically targeting any one of the six individuals who were murdered,” police spokesman Don Aaron said Tuesday.

While the motive remains under investigation, police say Hale at some point was a student at The Covenant School.

Hale graduated from Nossi College of Art & Design in Nashville last year, the president of the school confirmed to CNN. Hale worked as a freelance graphic designer and a part-time grocery shopper, a LinkedIn profile says.

Police have referred to Hale as a “female shooter,” and at an evening news conference added Hale was transgender. Hale used male pronouns on a social media profile, a spokesperson told CNN when asked to clarify.

Armed with three firearms, the shooter got into the school by firing through glass doors and climbing through to get inside, where the shooter could be seen walking through the hallways and pointing an assault-style weapon, surveillance video released by Metro Nashville Police shows.

The first call about the shooting came in at 10:13 a.m. and police rushed to the school, arriving at 10:24 a.m., according to the police chief.

Police on Tuesday released body-camera footage from the two officers who opened fire on the shooter after rushing into the school on Monday.

The footage, from the body-worn cameras of officers Rex Engelbert and Michael Collazo, begins with Engelbert arriving at the school to find a woman outside who says the school is on lockdown but there are two children unaccounted for.

After the officer is given a key to open a door into the building, a group of five officers enter the school amid wailing fire alarms and immediately go into several empty classrooms rooms to look for the suspect.

As they clear the rooms, officers hear gunfire from upstairs and rush up to the second floor, where Engelbert, armed with an assault-style rifle, fired multiple times at a person near a large window, who dropped to the ground, the video shows.

Collazo then appeared to shoot the person on the ground four times with a handgun, yelling “Stop moving!” The officers then approach the person, move a gun away and radio “Suspect down! Suspect down!”

The shooter was dead at 10:27 a.m., Aaron said.

As a private school operated by a church, there was no school resource officer assigned by the city to guard the school, according to Aaron.

Asked about the roughly 11-minute gap between when police received the first call of an active shooter and when officers arrived at the school, the police chief told reporters, “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 and so there’s a lot of things that could have happened – traffic was locked down, etc.”

The victims of the shooting included three 9-year-old students: Evelyn Dieckhaus, William Kinney and Hallie Scruggs, the daughter of lead church pastor Chad Scruggs. Also killed were Cynthia Peak, 61, a substitute teacher; Katherine Koonce, the 60-year-old head of the school; and Mike Hill, a 61-year-old custodian, police said.

“Our community is heartbroken,” The Covenant School, a ministry of Covenant Presbyterian Church, said in a statement.

“We are grieving tremendous loss and are in shock coming out of the terror that shattered our school and church,” the school said.

Sissy Goff, one of Koonce’s friends, went to the reunification center after the shooting and suspected something was wrong when she didn’t see Koonce there.

“Knowing her, she’s so kind and strong and such a voice of reason and just security for people that she would have been there in front handling everything, so I had a feeling,” Goff said.

Peak, a substitute teacher, was best friends with Tennessee First Lady Maria Lee and was supposed to go over to the Lees’ home for dinner Monday evening, Tennessee Gov. Bill Lee said in a video statement Tuesday.

“Maria woke up this morning without one of her best friends, Cindy Peak,” the governor said.”Cindy and Maria and Katherine Koonce were all teachers at the same school and have been family friends for decades,” he added.

Some families of the victims have released statements as they mourn their loves ones. Hill was described as a father of seven children and grandfather to 14 who loved to cook and spend time with his family, his family said in a statement obtained by CNN affiliate WSMV.

Evelyn’s family released a statement calling her “a shining light in this world.”

The city of Nashville is planning a vigil on Wednesday night to mourn those lost in the mass shooting, according to Nashville Mayor John Cooper. It will take place at One Public Square park at 5:30 p.m. local time.

“It is important that we stand together on this dark day for Nashville,” he said in the tweet. The city has also set up a fund to help support the survivors of the shooting, Cooper said. — CNN