Medford Schools Security: One Question

I want to know what -- if anything -- prompted Mr Edwards (the principal) to "clean his office" the day after the gun magazine was found.

As WCVB reports:

"The magazine was found under a seat in the theater on Dec. 29, 2017, by a professional cleaning company, the district said. No firearm was found. It was turned over to the custodian, who locked it in Principal Jake Edward's office.

"While cleaning his office the next day, the principal believes he threw the magazine in the trash along with several other items, the district said."

http://www.wcvb.com/article/police-searching-again-in-school-where-gun-mag-was-found/18659343