Thai authorities said the attacker was believed to be Army Sub. Lt. Jakrapanth Thomma, of the 22nd Ammunition Battalion.
Authorities brought the gunman's mother from his hometown in Chaiyaphum Province to an area near the mall but she was unable to get inside, said Maj. Gen. Jirapob Puridet, who led the security team inside the building.
The mother, whose name was withheld, told him there was little point in talking to her son anyway, as he had depression and an extremely bad temper.
The gunman had a machine gun that he had stolen, with around 800 rounds of ammunition and two short guns, Puridet said.
Thai people check the news on a phone near the shopping mall where a mass shooting took place on Saturday in Korat.
"We had to make the move of confronting him because people who were trapped inside a freezing room sent messages to us that the oxygen level was very low and they are suffocating," Puridet said. "So we had to risk to confront him face to face otherwise people who were trapped inside would die."
One officer was killed and three others injured during the ensuing confrontation, Puridet said.
"It was almost like a Hollywood action movie shooting scene," he said. "At certain points the gun firing was nonstop."
Frantic scenes from the mall overnight showed heavily armed Thai soldiers trying to move terrified shoppers to safety.
News footage from the scene showed people leaving the area in pickup trucks and cars as security forces surrounded the mall.
Medics prepare to enter the Terminal 21 mall, where a mass shooting took place on Saturday.
Survivors described the desperate situation inside the shopping mall. "It was frightening because I could hear the occasional gunshot ... we waited a long time for the police to come and help us, many hours," Suvanarat Jirattanasakul, 27, told Reuters news agency.
The gunman was "aiming for the heads," another survivor told local Amarin TV, according to Reuters.
"He was shooting everywhere and his shots were very precise," said the man, identified as "Diaw" and whose colleague was killed.
At a morgue in Nakhon Ratchasima, the family of 13-year-old Ratchanon Karnchanamethee sobbed as they identified his body.
"He's my only son. He hasn't even had dinner," said his father, Natthawut Karnchanamethee. "I allowed him to do anything he wanted to. I never set expectations for him. I only wanted him to be a good person."
Earlier Sunday, Thailand's Prime Minister Prayut Chan-o-cha said the rampage was sparked by an argument the gunman had at his base with another soldier over a land-selling commission fee. He added that the gunman had taken hostages during the later standoff but didn't elaborate on how many or what happened to them.
"In general, any military (officer) would be good at guns, but this man certainly has more skills," defense ministry spokesman Lt. Gen. Kongcheep Tantravanich said.
After shooting his fellow officer at the base, the gunman took his gun and shot other soldiers. It wasn't immediately known whether how many military personnel were killed.
After the shooter left the military base, he drove to the shopping mall in a military Humvee that he had stolen, shooting civilians along the way, Tantravanich said.