You happen to be at the library at the same time as this was happening. Jeannie and Frank are waiting in the cafeteria, probably discussing about Frank's crush Veronica. You see Lucas being bullied by Billy. Billy also used to bully you when you were in his section. He has a strong body build due to which he is able to overpower others. He sees Billy raising his fist to hit him. Others who are watching are doing nothing since they all are afraid of him.