72-year-old Bulger is the government 's star witness against John Martorano . Bulger turned his head , seeming to look at his former friend sitting just six feet away , only when Martorano said he learned Bulger was an FBI informant . Martorano has admitted to six murders as part of Boston 's Winter Hill Gang . He testifies that Bulger was directly involved in some killings . `` A serial killer kills because they like it ... I never had any joy in it , '' Bulger says .
72-year-old Bulger is the government 's star witness against John Martorano . Martorano has admitted to six murders as part of Boston 's Winter Hill Gang . He testifies that Bulger was directly involved in some killings . `` A serial killer kills because they like it ... I never had any joy in it , '' Bulger says .