(1) At the end of each investigation of a complaint, the commission shall prepare a final investigative report containing:
(a) The names and dates of contacts with witnesses;
(b) A summary and the dates of correspondence and other contacts with the aggrieved person and the respondent;
(c) A summary description of other pertinent records;
(d) A summary of witness statements; and
(e) Answers to interrogatories.
(2) A final investigative report may be amended if additional evidence is later discovered.