how can I kill a session who's status is "KILLED"?

HI ALL:

     In Oracle 8.0.3 Server,there are a session who's status is "KILLED",
        I Need to kill this session because it lock a table,
        but when I try to kill this session,
             "ALTER SYSTEM KILL SESSION 'sid,serial#';
          and get the following error message:
             ORA0---31:session marked for kill,
        and this session still reside in the databse,
          Can anyone tell me how to kill this "KILLED" session.
        Thank You in advance.