It appears that the Fresno Unified School District had a breach involving employee data a few years ago, but only discovered it now. Even now, however, they do not yet seem to know exactly how or when the breach occurred.
From their notification letter:
On July 5, 2017, Fresno Unified contacted the Gilroy Police Department to confirm the arrest of three individuals in Gilroy, California, who were in possession of unauthorized personal information of Fresno Unified employees. On July 6, 2017, it was confirmed that the personal information obtained included that of 53 employees, retirees and their dependents and the information obtained was a few years old. On July 10, 2017, the Clovis Police Department arrested a separate individual in Clovis, California, who was in possession of unauthorized personal information related to Fresno Unified employees, retirees and their dependents.
Police are unclear as to how the information was obtained, but at this point in their investigations, authorities have indicated the two incidents are related.
Given the aforementioned law enforcement investigations did not formally require delay of this notice, Fresno Unified proceeded to provide this notification in an expeditious manner.
What information was involved?
The individuals affected include employees, retirees and their dependents. The personal information potentially compromised includes name, address, phone number, birthdate, and Social Security number.
You can access the template of their notification letter on the California Attorney General’s site.