It happened shortly after 10 a.m. at the JP Morgan Chase Bank in Hamilton Township.
The FBI says the robber entered the bank, approached the teller counter, waived and pointed a silver revolver at the teller and fired. He escaped on foot with an undisclosed sum of cash.
The robber is described as a black male who was wearing a black ball cap, blue jeans, dark glasses, black gloves, tan work boots and a dark blue long sleeve shirt.
The FBI says the teller is undergoing surgery. Authorities have not released the teller's name.