One of three men who were working at a development across from the supermarket was using the .22-caliber tool, Montvale Police Chief Joseph Sanfilippo said.
The gun fires nails into concrete, masonry or steel.
Police quickly -- and cautiously -- responded to the call shortly before noon.
The matter was promptly resolved, the chief said.
Click here to follow Daily Voice Drexel Hill-Upper Darby and receive free news updates.