Shannon McKillen was a member of the Irish Mafia.
Much like her twin sister, Erin, Shannon attended school with Bruce Wayne, becoming good friends with the distant orphan. Upon growing up, Shannon, much like Erin, married into the McKillen Family, becoming of the Irish Mafia. Upon the death of Erin's husband, Shannon helped her sister lead, but, despite her criminal ways, was sent to prison by Harvey Dent through illegal methods. Deciding to kill herself, Shannon's death allowed Erin to break out of prison and leave Gotham City behind.