The province's Special Investigations Unit says the officer involved in the shooting of a 62-year-old man in Mississauga last month, has declined to be interviewed or turn over his notes.
The SIU says it is his right to do so.
Investigators say they have made substantial progress in investigating the death of Ejaz Choudry, but they still need to speak with the man's family.
The agency says nine officers deemed to be witnesses have been interviewed.
Peel Regional Police shot and killed Choudry in an apartment building on June 20 after performing a wellness check.