/**
  * Removes volunteer(row) from table and database
  *
  * @param rowNum
  */
 public void removeVolunteer(int rowNum) {
   DbManager.remove(rowNum, DbManager.VOLUNTEERS);
   data.remove(rowNum - 1);
   fireTableRowsDeleted(rowNum - 1, rowNum - 1);
   // shift ID
   for (int i = rowNum - 1; i < data.size(); i++) {
     data.get(i).setAttribute(0, Integer.parseInt(data.get(i).getAttribute(0).toString()) - 1);
     fireTableCellUpdated(i, 0);
   }
 }