It happened around 8:30 Saturday morning at the PNC East Ambler Branch on the 1000 block of Bethlehem Pike.
Authorities say right after the bank opened for business, the suspect walked in armed with a pistol. He was wearing a white cloth bag or pillowcase over his head with eye holes cut out.
The suspect ordered everyone down to the floor and put and undisclosed amount of cash into a black Nike drawstring bag.
No shots were fired and no one was physically injured.
The gunman then fled the scene on foot and headed north on Bethlehem Pike.
Police say it's possible that the man fled into a nearby alley and left in a vehicle.
The alleged bandit is described as a white male, 5'10" to 6'0" tall, 210 pounds with a heavy build.
He was last seen wearing a brown suit coat, brown or grey patterned tie, a light blue button down shirt, dark pants and light green latex or rubber gloves.
Anyone with any information about this robbery is asked to call the Upper Dublin Township Police Department at 215-646-2100 or the FBI at 215-418-4000.
