Hi,
you can get the list of users from the DB. Display the users and make sure that your checkbox value should identify the user_id ( may be whatever u can identify your user as unique ).When multiple users are selected,then in the CGI you can get it (user ids )in the array-context .If your db supports sub-query then, you just do,

  delete from tbl_name where id in (join(',',@usr_id_array));
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Oterwise, you just prepare a delete query (outside the loop )and execute the query in the for loop for each user id.
This will delete all the users from the db.
-kulls.