A Collingwood, Ont., man died as a result of being shocked with a Taser but the officer who pulled the trigger was not responsible for his death, Ontario's Special Investigation Unit has concluded.

In a report released Monday, the province's independent investigation agency conceded the Taser, a controversial policing device that incapacitates its target with electric shocks, directly caused the death of Aron Firman in June.

"The Taser's deployment in my view caused Mr. Firman's death," SIU director Ian Scott said in a statement.

Firman, a 27-year-old resident of a group home in Collingwood, died after being Tasered by an officer from the Ontario Provincial Police's Collingwood detachment who had been called to the home for an assault complaint.

Scott said he was willing to concede that the Taser shock caused the man's death, but determined the officer was conducting a legal arrest at the time and responded appropriately.

"There are no reasonable grounds to believe that the subject officer committed a criminal offence in relation to the death of Mr. Aron Firman," Scott said.

On June 24, two OPP officers were dispatched to the Blue Mountain Residence in Collingwood to investigate an assault. The officers found Aron Firman sitting in a chair outside one of the buildings.

According to an SIU report released Monday, the officers attempted to speak with Firman without success. He became agitated when the officers attempted to take him into custody, striking one officer in the face with his elbow.

The SIU concluded that Firman then moved toward the other officer, who shot him with his Taser. Firman was able to take a few more steps before falling to the ground unconscious. He was taken to the Collingwood General and Marine Hospital where he was pronounced dead.

A post-mortem found Firman had died from "cardiac arrhythmia precipitated by electronic control device deployment in an agitated man." The coroner added that it was possible underlying health conditions played a factor.

Scott said the Taser is considered a "less lethal" weapon, but in this incident it had caused Firman's death.

"However, the subject officer could have reasonably thought that the Taser deployment would not be lethal based upon his training," Scott said. "In these circumstances, and in light of Mr. Firman's demonstrated degree of aggression, I am of the opinion that the Taser's deployment was not excessive, notwithstanding the fact that it caused Mr. Firman's demise."

The investigation, conducted by a total of six SIU investigators, included interviews of one subject officer and four other officers as witnesses. Investigators also spoke with 23 civilian witnesses.

The SIU investigates incidents involving police that result in serious injury or death, or where there have been allegations of sexual assault.