When the suspected shooter drove into the parking lot of Nashville's Covenant School at 9:53 a.m. local time on Monday, a maintenance worker was standing outside with a leaf blower and a group of children were at a playground, some enjoying the sunny spring morning on a swing set, according to security video from the hilltop campus.
The suspect, identified as 28-year-old Audrey Hale, circled the nearly empty parking lot in a four-door Honda Fit, driving by the playground before parking.
Hale sat in the car composing an Instagram message to Averianna Patton, a former middle school basketball teammate, and sent the message at 9:57 a.m., writing, "I'm planning to die today. THIS IS NOT A JOKE!!!"
"You'll probably hear about me on the news after I die," Hale wrote, according to the message Patton shared with ABC News. "This is my last goodbye. I love you," Hale wrote, adding a heart emoji. "See you again in another life."
Hale once attended the Covenant School, a preschool to sixth-grade institution run by the Presbyterian church, and did not have a criminal record. But law enforcement officials said medical professionals treated Hale for an emotional disorder.
Nashville Police Chief John Drake said Hale left home on Monday morning with a red bag. Before walking out the door, Hale's mother asked what was in the bag, Drake said.
"I think she just dismissed it because it was a motherly thing and didn't look in the bag because, at the time, she didn't know (the suspect) had any weapons and didn't think any differently," said Drake, adding that the investigation revealed Hale had purchased seven weapons, including two assault-type rifles and a pistol Hale was armed with during the rampage that left three adults and three 9-year-old children dead.
School surveillance video captured the suspect at 10:10 a.m. using one of the high-powered rifles to blast through the locked glass doors on the side of the school and stepping through the broken glass to enter the main school building.
Drake said the school custodian, 61-year-old Mike Hall, a father of seven children and a grandfather to 14, was standing in the hallway and was fatally struck by at least one of the shots the suspect fired through the glass entrance doors.
Other security video clips from inside the school showed the suspect walking by the church office before circling back and briefly entering the apparently empty office through an unlocked door and emerging, pointing the barrel of a gun down the hallway and then going through a set of unlocked double doors.
Drake said the suspect encountered Katherine Koonce, the head of the Covenant School, outside of Koonce's office. The chief said Koonce was fatally shot in a hallway after possibly getting into a confrontation with the shooter.
Police said that at 10:13 a.m. someone from inside the school called 911, reporting shots fired.
The hallways, offices and classrooms, according to the videos, appeared empty as the suspect -- wearing a red ball cap turned backward, camouflage pants, sneakers, black gloves and wielding two assault-type rifles, one being held and the other slung over a shoulder -- walked around, entering doors.
At 10:20 a.m., a security video showed Hale walking down a hall, passing an office with a sign reading "Children's ministry."
"Based on what I know about the school and the neighborhood around it, those that fled would have been able to flee into some pretty serious cover and concealment areas pretty quick based on the terrain. But those that were not able to do that and locked down the building, from what I understand, did that correctly as well," Brink Fidler, president of Defend System, an active shooter training company that performed drills with staff at Covenant School last year, told ABC News.
While teachers hid with students in rooms and closets, others fled the campus on foot, according to witnesses.
Actress Melissa Joan Hart told ABC News she was driving near the school with her husband when they noticed children coming out of a wooded area and stopped to help.
"We helped a class of kindergarteners cross a busy highway. They were climbing out of the woods," Hart said. "They were trying to escape the shooter situation at their school. So, we helped all these tiny little kids cross the road and get their teachers over there. And we helped a mom reunite with her children."
Katie Robbins, who lives near the school, told ABC News she watched the chaos unfold from her window.
"My heart almost exploded," Robbins said. "Like, 'Oh my God, it's happening here."
Robbins said she saw a group of children and their teacher sprinting from the school, crossing the street and huddling at the gate outside her home.
"A little boy said, 'Help me get inside. How can I get inside?'" Robbins recalled. "I just wanted to help him and help all of them get inside, get away."
She said she and a neighbor helped them get out of harm's way.
The first officers arrived on the scene at 10:21 a.m. and entered the school two minutes later. Drake said 14 minutes elapsed between officers getting the first 911 call and when the suspect was killed.
Officer Rex Englebert, one of the first officers to arrive on the scene, immediately went to the rear of his police SUV cruiser and retrieved an assault-type rifle from a bag, according to footage from his body-worn camera that was made public on Tuesday.
"The kids are all locked down, but we have two kids that we don't know where they are," a school staff member is heard in the body-camera footage telling Englebert, as he approached the front door of the school.
The staffer relayed to Englebert a report she received over her cellphone from inside the school and instructed the officer how to get to the stairwell leading to the second floor, saying, "all the way down this hall. At the end of this hall is Scholarship Hall. They just heard gunshots down there, and then up the stairs are a bunch of kids."
Englebert went to the front door and was handed a key by another school staffer standing there, according to the body-camera video. Englebert called out for three officers to join him as he used the key to open the door, yelling, "Let's go!"
As Englebert and other officers entered the school, sirens were going off, according to the body camera footage. As the officers went classroom-to-classroom searching for the suspect and victims, one was heard yelling about the suspect, "We don't know where he is."
Then the officers heard gunshots. "Sounds like it's upstairs," Englebert is heard saying.
At least five officers are then seen going up a stairwell to the second floor at 10:24 a.m. as the gunshots grew louder. Englebert appeared to take the lead, followed by several officers, including officer Michael Collazo, who was armed with a handgun, according to his body camera video.
When they reached an open area, the officers spotted and engaged the suspect, who was standing near a broken window, at 10:25 a.m. Someone yelled, "Reloading" as Englebert shot the suspect and Collazo also opened fire. According to law enforcement sources, the suspect was killed at 10:27 a.m.
A police spokesperson told ABC News that Hale was assigned female at birth, identified as transgender, and pointed to a social media account linked to Hale that included use of the pronouns he/him.