My boss says that I stole money from her office- what should I do?

My boss’s office door was unlocked all day. I came to the school alone at night because I had forgotten my charger in my classroom. I have keys to the main office door and the classrooms. While I was there I went into the main office to use the restroom, and I also picked up a small cardboard box that had been placed by the garbage, to use as a shipping box. The next morning my boss accused me of stealing money from her office. some cash and some checks were missing. The checks were made out to the school, so I obviously couldn’t have used them. She said that she saw the footage of me coming in at night and leaving the office with something in my hand. She didn’t believe me when I said that it wasn’t just an empty box. I told her that any of the other employees could have taken it during the day. she doesn’t have cameras in the office. Only the hallway. Today an officer came in to looK at the footage and didn’t say anything to me. What do I do??