"The Breakfast Club" - Who Is Mr. Tierney?

which Vernon references while creeping the personal files in the basement. I thought he's supposed to be checking Bender's file, which would explain the remark about a history of mental illness, "no wonder he's so f ked up," adding depth to Bender's character, or motivation, as well as empathy for Vernon's. If you know the answer, how do you know?