Who is Buck in the novel, Easy?

Buck is one of Kennedy's fraternity brothers. He attempts to rape Jacqueline three times, targeting her because of his animosity towards Kennedy who was chosen as pledge class president instead of Buck. Luckily for Jacqueline, Lucas saves her from Buck's unwanted advances; however, when Buck rapes Mindi, Jacqueline and Mindi press charges so Buck cannot assault anyone else. The third time that Buck attempts to assault Jacqueline, he is in violation of a restraining order, so he is arrested and expelled.