Been to the bank....
A few years ago they installed an 'entry system' at the bank so you have to press a buzzer on the outside, the teller checks that you haven't got a mask over your head and a shotgun and presses a button to open the door....
The system has always been flawed because there is a button on the inside to let yourself out when you have finished your business. So a masked gunman only has to wait outside the door until somebody leaves before rushing in...
Now, presumably for some bizarre H & S regulation they have fitted another huge emergency exit door with a push-bar to open it which everybody now uses to leave (and enter if the timing is right) the bank...
bear in mind that the bank has just two positions and room enough for about five or six customers inside....