It is usually a good idea to provide a white reference. Whenever you light a "dark" scene, you want the viewers to feel like their eyes have adjusted to the darkness and can now see - which is exactly what our eyes really do. No camera made yet can duplicate the light sensitivity of the human eye. What we want to do in lighting is imitate what the human eye would see under these circumstances. When the eye dilates so wide that it can see into the dark, what would be a normal intensity light now looks extra bright - think about headlights at night. During the day they aren't bright, but they are blinding at night. So, to sell the night break in look, provide some sort of "bright" white reference somewhere in the background. It can be justified as light from a streetlamp outside, shining in. It could be something as simple as car headlights or an outside house light outside a window. It could be the burlgar's flashlight. Overexpose that source and light the scene so tat the audeince can see what is going on - unless you want something more expressionistic or surreal.
Also consider your color temperatures. Do you want the flashlight white, the fil a litttle cooler and some streetlight source coming in the background to be warm? As others have said, you might consider the Lee urban colors or the Rosco sodium vapor gel color to add that odd color we often see at night.
I certainly wouldn't limit myself to using only one light. that might work, but you might want to use a very soft low intensity 1/4 CTB fill and then add some inkies or Arri 150s or the new tiny LED hard lights made by cineo, dedo, frezzi or Litepanel - or even cheaper, use a LED flashlight to provide the "bounce" off the steel of the vault onto the faces of the thieves. This might add more texture to the over all look. Just because you can do it with one light doesn't mean that will provide the best look - it might - but you might want to paint the light a bit more as well.
Good luck - and have fun with it.