The suspect in was arrested earlier this year for allegedly threatening on Facebook to shoot his older brother in the head "and not think twice about it," according to a police report obtained by CBS News.
Michael Brandon Hill, 20, faces multiple charges after police say he slipped into Ronald E. McNair Discovery Learning Academy Tuesday with an assault rifle and other weapons and held one or two staff members in the front office captive.
A Henry County police report obtained by CBS News Wednesday shows that Hill's older brother, Timothy Hill, told police last New Year's Eve that threats Michael made a day earlier made Timothy "fear for his life."
"Mr. Hill advised his brother stated on Facebook that he would shoot him in the head and not think twice about it," a police officer wrote in the report.
Timothy Hill told police that he knew his younger brother had "mental issues" and was under a doctor's care but that he didn't know where Michael was living at the time.
More than two months later, in March, Michael Hill turned himself in on the outstanding warrant for making "terroristic threats."
On Tuesday, as officers swarmed the elementary school campus, DeKalb County Police Chief Cedric L. Alexander said he. Michael Hill then surrendered. No one was injured.
CBS News correspondent Mark Strassmann reported on "CBS This Morning" Wednesday from Decatur, Ga., that authorities say Hill was armed with an AK-47 and other weapons and likely entered the building through the front door behind someone authorized to be there. He held two employees hostage while he terrorized the campus, firing his rifle into the air from inside the front office.
But Hill never got past the front office. School bookkeeper Antoinette Tuff says she was one of the hostages.
In an interview on ABC News, Tuff said she worked to convince the gunman to put down his weapons and ammunition.
"He told me he was sorry for what he was doing. He was willing to die," Tuff told ABC.
Speaking Wednesday on ABC, Tuff said the suspect told her he hadn't taken his medication.
She told him her life story, about how her marriage fell apart after 33 years and the "roller coaster" of opening her own business.
"I told him, 'OK, we all have situations in our lives,'" she said. "It was going to be OK. If I could recover, he could, too."
Then Tuff said she asked the suspect to put his weapons down, empty his pockets and backpack on the floor.
"I told the police he was giving himself up. I just talked him through it," she said.
Hill is charged with aggravated assault on a police officer, terroristic threats and possession of a firearm by a convicted felon. Police questioned him for hours at headquarters. There was no information on a possible court date. Alexander said police were unsure of Hill's motive and that Hill, who had an address listed in court records about three miles from the school in Decatur, had no clear ties to the school.
A woman answering the phone at a number listed for Hill said she was his mother but that it wasn't a good time and rushed off the phone.
Tuff told WSB-TV in Atlanta that she tried to keep Hill talking to prevent him from walking into the hallway or through the school building.
"He had a look on him that he was willing to kill matter of fact he said it. He said that he didn't have any reason to live and that he knew he was going to die today," Tuff said, adding that Hill told her he was sure he'd be killed because he'd shot at police officers. "I knew that if he got out that door he was gonna kill everybody," she said.
Dramatic television footage showed lines of young students racing out of the building with police and teachers escorting them to safety. They sat outside in a field for a time until school buses came to take them to their waiting parents and other relatives at a nearby Wal-Mart. As each bus arrived a couple hours later, cheers erupted in the store parking lot.
Rufus Morrow was one of those parents and held his 10-year-old daughter close to him during an interview after the two were reunited.
"My stomach was in my throat for the whole time until I saw her face on the bus," he said.
His daughter, a fifth-grader, told The Associated Press that a voice came over the intercom saying school was under lockdown and instructed students to get under tables. She said her teacher told the class to sing and pray.
"There were a lot of girls crying, I was feeling scared but I didn't cry. I was just nervous," she said.
Tuff called WSB-TV as it was happening to say the gunman asked her to contact the Atlanta station and police. WSB said during the call, shots were heard in the background. Assignment editor Lacey Lecroy said she spoke with Tuff, who said she was alone with the man and his gun was visible.
"It didn't take long to know that this woman was serious," Lecroy said. "Shots were one of the last things I heard. I was so worried for her."
Complicating the rescue, bomb-sniffing dogs alerted officers to something in the suspect's trunk and investigators believe the man may have been carrying explosives, Alexander said. Officials cut a hole in a fence to make sure students running from the building could get even farther away to a nearby street, he said.
The school has about 870 children enrolled. The academy is named after McNair, an astronaut who died when the space shuttle Challenger exploded on Jan. 28, 1986, according to the school's website.
As they waited for their children, many of the parents said they were surprised that anyone could get into the school. Many of them recounted having to ring a buzzer at a door with a camera to get in to drop off or pick up their children.
Students at the school arrived Wednesday morning at nearby McNair High School, where they would attend classes for the time being. The high school's marquee said "Welcome McNair Elementary School Our Prayers Are With You."