Seemingly… well unrelated

This sign hangs at the entrance to a subway station, inside after one has proceeded through the ticket turn style.  It appears comical, how does someone stealing your purse or lifting your wallet, set off the light to begin flashing? The mezzanine, referred to in the sign, just happens to be around a long corner and down a flight of stairs.  Does anyone even know what a mezzanine is anymore?  And if the light is flashing, are you going to proceed further?  Check it out?  Get the facts?  I don’t think so.  Run like hell would be more like it. Who thought up this one?