How to send Workflow Notification to a specific Representative after the rejection of approvals

We have an approval chain for any HR workflow, in any step of the approval, once an approver rejects, a specific representative of the worker must get a notification.

We've first tried to do that in BPM, but we cannot add notification over there that will trigger only from"rejection". Furthermore we cannot add "representative" as a notification recipient.

The second thing we've tried was adding the representative as a "FYI step" at the end of the workflow in approval rule graphical tool. But this time, once any of the approvers in the earlier steps of the chain rejects it, the approval never reaches to the last step so it doesn't trigger a notification to the representative.