Hi, it's not normally considered best practice to 'delete' records/data and a better solution would be to set them as inactive\cancelled etc.
If you must delete a record, then it no longer exists so cannot be used for reference, and I would think a before delete BR to trigger a sysevent, ensuring that the any values you require for your notification (or script action) are included as event parameters - as you will need to utilize these as your source record will be gone.
