Move a box on the shelf to expose a grill, open the grill.  Through the grill you will see a man reading a newspaper.   Load your crossbow with an ice-dart and shoot the man.

Cover your tracks by closing the grill and putting the box back into it's place.

Open the case and then open a small compartment inside.   There are tow pieces of paper take the first one only.   This gives you a clue to how to open the vaults later on (read it carefully, include the printed wording as well as the hand-written).

Exit the workroom and head down the corridor towards the security room.