(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.