(CNN) —-
An employee at a Subway restaurant in Atlanta was shot to death Sunday after a customer became upset about a condiment on her sandwich, Atlanta police said.
Police were called to the restaurant near Mercedes-Benz Stadium in downtown Atlanta shortly after 6:30 p.m., according to a police department news release.
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Agents found two employees with gunshot wounds, and a woman was later pronounced dead at a hospital.
"This was a very tragic situation that didn't have to happen," Deputy Chief Charles Hampton Jr. said during a news conference Monday.
"The suspect entered the restaurant (to) order a sandwich and there was something wrong with the sandwich that upset him so much that he decided to take his anger out on two of the employees here."
A 36-year-old man was arrested Sunday night, Hampton said.
He declined to identify the suspect citing the ongoing investigation.
Hampton said the suspect used a gun during the incident.
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The medical examiner identified the victim as 26-year-old Brittany Macon.
An autopsy has not been completed, but the preliminary cause of death is gunshot wounds, Bertram Ennett, an investigator with the Fulton County Medical Examiner, told CNN.
A 24-year-old woman who was also shot is in critical condition, police said.
His 5-year-old son was also in the store at the time of the shooting.
Hampton said the dispute was over the excess mayonnaise in the sandwich, but stressed that the focus should be "on the gun violence," not the mayonnaise.
"It just breaks my heart to know that someone has the audacity to pull a gun and shoot someone for just putting too much mayonnaise on a sandwich," Willie Glenn, co-owner of that Subway, told CNN affiliate WSB.
"They were just model employees," Glenn told WSB.
Subway is about to make the biggest menu revamp in its history.
A Subway spokesperson said: "Our deepest condolences to the families and friends of those attacked in what was a senseless act of violence. At this time, our primary concern is for the franchisees' team members and customers who They were inside the restaurant.
There have been 74 homicides in the city of Atlanta since the beginning of the year, according to the latest data release from the Police Department.
That's a 19% increase from the same period last year, the department said.
CNN's Ryan Young contributed to this report.