The director of Ontario's special investigations unit (SIU) says there are no reasonable grounds to believe three Ontario Provincial Police officers committed a crime when they shot a 40-year-old man in November.

As CBC Hamilton reported at the time, the man had barricaded himself in a home on Chiefswood Road in Ohsweken, Ont. which is part of Six Nations of the Grand River, and repeatedly fired a gun at police.

The incident began on Nov. 1 around midnight when Six Nations police received a call about the man they would eventually shoot, SIU director Joseph Martino wrote in a report. He had reportedly confronted local "security personnel" at a business with a rifle and knife, but did not fire his gun at the time. Whoever the man confronted reported he said it was "open season" on police, Martino said in the report.

The man then went into a trailer and Six Nations police called the local OPP detachment, which is based in London, Ont. The report said OPP officers attempted to "resolve the situation," but the man would not leave the home and surrender. Police used tear gas to attempt to drive the man outside, and rammed his trailer with an armoured vehicle. The man shot at police, hitting the armoured vehicle, and shot down a drone.

Eventually, using smoke and the armoured vehicle, police forced the man outside. Martino writes that the man shot an officer in the head, and in response, police shot him multiple times using bullets and anti-riot rounds, which the report describes as being less lethal. The man survived and an ambulance took him to Hamilton General Hospital.

The report details forensic evidence investigators collected, including the helmet the officer who was shot wore. It notes the material inside the helmet "bulged" but it's unclear if the officer was hurt.

The SIU investigates incidents involving police officers, special constables of the Niagara Parks Commission or peace officers under the Legislative Assembly Act that may have resulted in death, serious injury, sexual assault or a weapon being fired at someone.

Investigators interviewed the man who was shot a week after the incident. They also interviewed civilian and officer witnesses. The three officers whose conduct was under review declined to be interviewed or share notes, which they have the right to do.

The report details videos filmed by witnesses, and Facebook posts the 40-year-old man presumably made during the incident, one of which "accused the OPP and Canadian government of assaulting him and breaking the law."

Martino wrote the man "was of unsound mind" and "believed himself to be an investigator and OPP officers murderers."

In deciding to clear the officers of any criminal wrongdoing, Martino writes officers resorted to weapons only after being shot at, and that it was clear the man was intent on shooting an officer. "Faced with a lethal threat, it is apparent that the officers acted to preserve themselves from grievous bodily harm or death."