Police in Boise, Idaho have arrested a 74-year-old woman after she was spotted “pouring mayonnaise in the Ada County library’s book drop box,” reports an Associated Press wire story. Police say the woman is “a person of interest” in “a yearlong spree of condiment-related crimes.”

According to the AP, “the woman is under investigation for at least 10 similar cases of vandalism since May 2009. Library employees have reported finding books in the drop box covered in corn syrup and ketchup.”

Another report, from the Idaho Statesman, fills in some key info the AP left out, such as the woman’s name (Joy L. Cassidy), and the fact that she was also carrying a loaded handgun.

No one seems to have any idea at all of a motive, though.