Police said the employee, who fired a semi-automatic handgun, is in custody after turning himself in.
The victim and the suspect have not been identified.
Police said this does not appear to be a random shooting, but an ongoing dispute between the two individuals.
According to the mall's code of conduct, firearms and illegal weapons are prohibited.
"On a Sunday afternoon, just everyone out with their family doing some shopping, you just don't expect things like this to go on," shopper John O'Sullivan said.
Officials said the upper level of the west side of the mall will be shut down for several more hours as police continue their investigation.
This is an ongoing investigation. Check back with wsoctv.com for more information.