ST. JOHN'S, N.L. -- A public inquiry report into the police shooting of a Newfoundland man has found the officer's use of force was appropriate, but found serious flaws in the RCMP's investigation of the death.

Inquiry Commissioner Leo Barry's report released Tuesday said the RCMP was correct not to charge Const. Joe Smyth of the Royal Newfoundland Constabulary for the killing on Easter Sunday 2015.

Smyth told the inquiry he shot Don Dunphy twice in the head and once in the chest after he suddenly aimed a rifle at him at his home in Mitchell's Brook, about 80 kilometres southwest of St. John's.

Barry said although Smyth showed "certain errors of judgment" and strayed from his training, there's no evidence to refute his argument he acted in self-defence.

"Despite some troublesome aspects of his testimony, I received no evidence to refute his version of events and there is forensic evidence to support it," he said.

He added: "It would be improper speculation to decide whether Const. Smyth may have avoided the need to use lethal force had he not made these errors."

Barry said Smyth was in Dunphy's house without lawful authority, because he had not given him enough information about why he was there.

Smyth was a member of then-premier Paul Davis's security team and visited Dunphy alone and unannounced after Davis's staff flagged a posting on Twitter.

Barry found the tweet was not a threat, but warranted follow-up.

He said Smyth failed to keep his eyes on Dunphy, particularly his hands.

Barry also concluded there's no evidence to support a theory by Dunphy's daughter that Smyth may have mistakenly thought a stick her father kept by his chair was a rifle.

"One question which remains unanswered is what motivated Donald Dunphy to move from being a participant in a cordial conversation to an agitated state in which he pointed a rifle at the police officer and left no opportunity for de-escalation," said Barry.

"Unfortunately, this question remains unanswered after considering all interviews, hearings, witnesses, and exhibits."

Dunphy was an injured worker who often aired his disgust with the workers' compensation system -- and what he saw as political indifference -- on social media.

The report makes a number of recommendations, including that crisis intervention and de-escalation training be provided to all police officers in Newfoundland and Labrador, with mandatory requalification every three years.

Smyth was the only witness to the killing.

Barry recommended such incidents be investigated by a civilian-led agency as in other provinces.

He said there were "material deficiencies" with the RCMP probe of the shooting, saying it "created the appearance of preferential treatment."

Barry told a news conference that he felt the RCMP probe was "less than robust," particularly in early stages as the Mounties tested the credibility of Smyth's story.

"They could have pushed more strongly," he told a news conference.

RCMP investigators admitted to the inquiry they were too familiar with Smyth as a fellow police officer whom many had met.

One in particular revealed to Smyth a day after the shooting that the .22-calibre rifle found at the scene was in fact loaded, telling him: "You saved your life."

"This was a very tragic incident," said provincial Justice Minister Andrew Parsons. He said he met with Dunphy's daughter, Meghan, earlier Tuesday to personally deliver the more than 500-page document.

Parsons said he can't possibly put himself in her shoes. But he said he hopes the report will show the governing Liberals are serious about answering how the shooting happened and to help ensure such a death isn't repeated.

"We need to restore public trust in policing and our justice system."

The inquiry cost almost $2.9 million.