The school's existing safety procedures will remain the same while the investigation takes place, Bolden said.
But he promised any needed changes will happen. "We will do everything humanly possible in our power to keep this next generation of learners safe."
Counseling was made available to the kids, and the school understands that some children might not be ready to come back right away, he said.
Inside the suspect's mind
On Wednesday night, Hill, 20, was in a Georgia jail awaiting a still undetermined initial court appearance.
Authorities are still hammering out exactly what charges he will face. Police spokeswoman Mekka Parish has said they would include aggravated assault on a police officer, terroristic threats and possession of a firearm by a convicted felon. Ray Davis, the lead detective on the case, added that false imprisonment and "several weapons charges" probably will be included as well.
Whenever the charges come down, Hill will waive his initial court appearance, said Claudia Saari, public defender for the Stone Mountain Judicial Circuit. She said members of her office's mental health division are handling his case and declined to make any further comment.
This week's incident is not Hill's first run-in with the law. He has a criminal history in DeKalb and neighboring Henry County that, while not "lengthy," does include violence, Davis said.
Specifically, Hill pleaded guilty in July to making "terroristic threats and acts" against his brother.
Henry County court records show that, in addition to three years of probation, he was ordered to attend anger management classes. But that county's district attorney, James Wright, said Wednesday that there's no indication that Hill completed them.
As to any connection to McNair Discovery Learning Academy, why he might have gone into it armed, and what he planned to do once there, authorities have not outlined a motive or a detailed plan.
Being from DeKalb County, Hill "possibly had been there (at the school) before speaking with some people in the administration," Davis said. But "there's no indication he had a grievance with the school."
Before he entered the school, the suspect took a picture of himself with the assault rifle -- which he'd taken "from the house of an acquaintance," said Davis, who did not say whether the weapon was stolen.
So did Hill go in intent on killing people?
Davis responded: "I believe there was something else, but I don't want to go into detail."
Some clues about his mindset are evident in the dramatic 911 call.
With Tuff acting as the intermediary on the call, the suspect said that "he should have just went to the mental hospital instead of doing this, because he's not on his medication."
Chief: It 'absolutely' could have been 'another Sandy Hook'
While Tuff seemingly kept her cool inside the school, a swarm of law enforcement was springing into action outside.
Police reacted "very, very quickly" -- including some officers who took up positions with long rifles -- "to engage the threat" and prepare for the worst, said Alexander, the DeKalb County police chief.
"We can all make a reasonable assumption that he came there to do some harm," he said, recalling last year's school massacre in Connecticut that ended with 20 students, six adults and gunman Adam Lanza dead. "He entered a school, an elementary school with children in it ... to do one of two things: Either to do harm to those children and/or any first responders."
Thankfully, that didn't happen.
In fact, the suspect never went beyond the school's offices and never near its classrooms. While he fired some rounds at police -- and one officer shot back at him -- no one was hit outside either.
And while there initially were fears that the suspect also had explosives, further tests indicated that was not the case: He came in with the rifle and a bag of ammunition, but no explosives.
Community members and leaders are offering praise for Tuff and police, as well as gratitude that the story did not turn tragic.