You walk through the north door to the vault area. You examine the filing cabinets, and you find hundreds of insurance, banking, loan, forms etc. If you have something specific to look for, feel free to specify it, but otherwise it just seems like a lot of legal mumbo jumbo.
You step into the office area. A teller sees you (you are in a well lit room, they are not, so you standout) and walks over to you and asks you what you were doing in the secure area
A guard arrives. He talks to the Teller you were just talking to, and you can make out that she is pointing at you.
It dawns on you that the broken window is in the staff room. A secure area. You could only know about it if you were somewhere you weren't supposed to be.