use this sql to check on the user how created the lock, and the sql statment that created that lock:
select a.object_name, b.oracle_username, b.os_user_name,c.sid, c.serial#,c.terminal, d.sql_text
from sys.dba_objects a,
where a.object_id = b.object_id
and c.sid = b.session_id
and c.sql_hash_value = d.hash_value
i think that kiling a session befor you know what was the resone s not that good. so check for the couse first. if you need to kill the session, the line goes like this:
alter system kill session 'c.sid, c.serial#'