Audit Trail report - which user's record was modified?

Summary

When choosing "Modify Enrollment Completion Status" how can I see whose record has been modified

Content

I need to do a monthly audit of:

1. who modified post-status of enrollments for the previous month
2. which enrollments the modifications took place within, and
3. which user's records had their post-status updated within that enrollment

I am able to pull all users who modified Post Status, and which enrollment it was modified within, but not which user's record was modified. How can I see this information? 

Thx