In the days since Paek's bloody rampage Tuesday, friends and colleagues of the family also have suggested finances were the likely source of the dispute.
Norcross police have identified the gunman as the 59-year-old Paek, and the victims as Byong Ok Kang, 64; Kum Hui Paek Kang, 61; Kum Sook Kim, 57, and Tae Yol Kim, 55.
Separately, the Associated Press reported Friday that Paek may be the same man who stood trial in Louisiana in the 1989 shooting deaths of three other men.
Jefferson Parish, La., officials said the file on the case was destroyed in 1994, but confirmed that records show a man named Jeong Soo Paek was acquitted of the slayings in Metairie. In those slayings, Paek was shot in the face and lost an eye.
The shooter in this week's spa slayings had the same name and was missing an eye. Summers was not able to confirm it was the same person but said he had heard Paek had been involved in a crime in Louisiana in the past.
Sang Pok Yi, 54, and his sons, Sang "Robert" Man Yi, 26, and Sung Tae Yi, 27, were fatally shot a home in the New Orleans suburb of Metairie. Jeong had worked for Sang Pok Yi in a building maintenance business.
In court testimony reported by The Times-Picayune at his trial in 1990, Jeong said the men became hostile toward him when he told them he might start his own business. He said he was beaten, and fired a .45-caliber pistol when he thought one of the men was about a draw a gun. It was never established which gun the bullets that wounded Jeong came from.
Several jurors said there was not enough evidence to support finding Jeong guilty of murdering the men.
In the Tuesday shootings, all four of Paek's victims were co-owners of the Su Jung Health Salon, which opened in 1998. The spa was meant to be a sanctuary for its customers, with steam rooms, water fountains, a cafe and comfy recliners among its many amenities.
Dave Weigel and his wife, Sung Chu, said Paek, a longtime friend, supplied his family members hundreds of thousands of dollars to help open the spa. But the family prevented him from taking an active role in the business, they said.
Weigel said Paek, a married father of three grown children, traced the exclusion to a brutal attack in New Orleans about 25 years ago. Paek lost one of his eyes and needed reconstructive surgery "basically to rebuild his whole face," he said.
"The rest of his family ... they were beautiful people, and they really shunned him after that," Weigel said. "Then, they excluded him from the business and told him they didn’t want him around because it was bad for business. He didn’t fit in."
Recently, Paek decided to start his own spa in Conyers.
He obtained a business license from the city in January and was poised to open Spa World in the 1100 block of West Avenue. In a letter to the city's planning and inspection services department, Paek said he planned to focus solely on massage therapy at his new business.
On an occupation tax form, Paek listed his sister -- and one of the victims -- Kum Hi Song as an emergency contact.
Signs announcing the grand opening are still on the spa's storefront, Summers said.
With the business ready to start accepting customers, Weigel said Paek was down to his last few dollars. Paek went to his family in recent days seeking financial assistance to make it through a rough stretch, the friend said, but the man was rebuffed.
"He literally needed money to eat," Weigel said. "I really wish he had come to us."
A message left at Paek's home in Buford wasn't immediately returned Friday.
Meanwhile, Gwinnett County's tight-knit Korean community has come together to cover the costs of the victim's funerals.
Travis Kim (no relation to the victims), president of the Korean-American Association of Greater Atlanta, said services for Kang and Song were scheduled for Saturday at Lee's Funeral Home in Decatur. The remaining family members, including Paek, will have their funerals Sunday at the same site.
-- The Associated Press contributed to this article.