During their fight, Steve inadvertently removes a latex mask from Amos's face, revealing him to actually be Principal Kastleman in disguise. Kastleman explains how years ago, Kathy discovered she was pregnant with Steve's child, after which Kastleman murdered her in a rage and hid her body in the school basement before killing multiple students. Callie and Steve manage to overpower Kastleman, impaling him with a javelin.
As the fight unfolds, Steve inadvertently exposes Amos's true identity as Principal Kastleman in disguise. Kastleman then reveals a dark secret from the past: he murdered Kathy, who was pregnant with Steve's child, and hid her body in the school basement before killing several students. Callie and Steve ultimately triumph over Kastleman, using a javelin to bring him down.