There are 3 cops, 2 on the first floor and 1 down next to the vault door. If you have no stars and you have cuffs, you should arrest the cops. This usually is the best option, because they won't respawn and kill you after you are done.

If you don't have cuffs, you can shoot the cops. But be careful, if you kill them, they are going to respawn in 10-20 seconds. If you get lucky and/or your aim is good, just shoot them until they drop, but won't die.

3rd and final cop downstairs shouldn't be a problem, unless you are slow or you have bad aim.