Police were called to the store on Henry Street in Roosevelt Park about a fight at about 3:30 p.m. Dispatchers then received a second call that an employee was down.
The woman was taken to the hospital, where she was pronounced dead, Roosevelt Park police said.
Police said they have reviewed surveillance tapes that show the fight started outside and moved inside the store. No employees were involved in the fight.
Police said the video also shows the female employee was moving toward the fight when she collapsed. Police said the woman did not make any physical contact with those involved in the fight.
No one was arrested in the fight.
An autopsy is being performed to determine the cause of death. The woman's name was not released.