Write SQL query to solve given problem: At which district did the multiple homicide case number JB120039 occurred?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT T1.district_no, T1.district_name FROM District AS T1 INNER JOIN Crime AS T2 ON T1.district_no = T2.district_no WHERE T2.case_number = 'JB120039' GROUP BY T1.district_no, T1.district_name