Report on shared records

Hello

I have a business case were the managers need to extract a report to identify the accounts and/or contacts group by user, where the user is either the owner of the record or the user to whom the record has been shared with. Please note that the records are visible by owner, that said, is a private model.

i.e

• Contact A is owned by Sales Rep 1 (only that sales rep has visibility on it)
• Sales Rep 1 shares contact A with the Sales Rep 2 granted read-only rights (now both Sales Rep 1 and Sales Rep 2 can see the record)
• Both sales reps have the same manager
• Manager wants to have a list grouped by sales rep to track which are the records they have to work on. Expected result should be as follows:
  • Sales Rep 1: Contact A, Contact M, Contact Z
  • Sales Rep 2: Contact A, Contact X, Contact L

Any help on how to achieve above will help me a lot! 

Thanks!