A Thief Among Us

There is a thief in our school building.
This thief comes in after hours.
Once the door is closed and locked.
The thief comes in dressed as a cleaning person.
The thief sweeps (well... sometimes that is questionable) and mops (or is supposed to).
The thief empties the trash and puts a new bag in nightly.
But....
The thief also took $5 that a student brought in for raffle tickets.
The thief took $4 that was sitting on my counter for 2 WEEKS untouched.
The thief recently took two bites out of a cheese block I had left in my fridge after a bridal shower.
The thief also took a Coke (OUT OF MY FRIDGE) that I had opened and drank out of since I drink one Coke over several days.
The thief took my cheese stick (OUT OF MY FRIDGE).
The thief has not just taken from me, they have taken from many others in my building.
Then, an experiment....  I left a donut on my counter, on purpose, Friday when I left school.
Then, the thief struck again.