Upper Merion Township police said the incident began when the woman was involved in an argument with three other women near the Five Guys.
The woman said she walked away to wait for her food, but was approached by two of the other women as the argument continued.
The single female said she believed she was about to be assaulted, so she pulled out a handgun from her purse and pointed it at them.
No shots were fired, police said.
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"All of a sudden, we see a couple of hundred people running toward us from the food court and we're looking and a guy runs by us," said David Ogleton of Devon. "I don't think he wanted to scare anybody else so he kind of just made the sign of a gun."
Ogleton said he was back to school shopping with his 11-year-old son.
As police made their way into the mall, stores began to lock down.
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Officer said shoppers and staff were shaken.
"I called my wife and we were saying this is not one of our worst fears but something that we're always worried about now," Ogleton said.
According to authorities, the woman who produced the gun did possess it legally and has a permit to carry a concealed weapon in Montgomery County.
Police said at this time, no charges are being filed.
No injuries were reported in the incident.