The investigation body formed by the Home Ministry will submit its report on September 7 (Monday) over the killing of Major (retd) Sinha Md Rashed Khan in Teknaf.
Chattogram Additional Commissioner Md Mizanur Rahman, who led the probe, confirmed the matter in a press briefing Saturday.
The 80-page probe report is complete, including a 12-point set of recommendations, he said.
"The probe body talked with 68 people, collected information from the spot and also visited spots where Sinha recorded his video documents," Rahman said.
The report contains the details over why the murder was committed and who was behind it, he said.
The body led by Mizanur Rahman was formed on August 3, and initially was scheduled to submit its report within seven working days, but received several extensions.
The probe body earlier interrogated the prime accused former Officer-in-Charge of Teknaf Model Police Station Pradeep Kumar Das on Wednesday.
Major (retd) Sinha was killed in police firing at Baharchhara police check-post on July 31.
Sharmin Shahriar Ferdous, elder sister of Sinha, filed a case with Teknaf Senior Judicial Magistrate's Court on August 5.