code: public static void bulletinOff(Bulletin bulletin, Level level, String message) {
          if (bulletin == null)
              return;
          synchronized (bulletins) {
              bulletins.remove(bulletin.getId(), bulletin);
          }
          try {
              WebSocketMessenger.getInstance().send("SystemMessage", bulletin.off(message).getJson().toString());
          }
          catch (IOException ex) {
              logger.warnException("Unable to publish to websocket", ex);
          }
      }
docs: Should be the same instance or have the same id as the bulletinOn message.