ST. JOHN'S, N.L. -- The police officer who shot and killed a man in his Newfoundland home used faulty judgment but appropriate force, says an inquiry head who chides the RCMP's "less than robust" probe.

Inquiry Commissioner Leo Barry's report Tuesday says the Mounties were right 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 Smyth showed "certain errors of judgment" and strayed from his training. Still, there's no evidence to disprove his claim he acted in self-defence, the report concludes.

"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 found Smyth was unlawfully in the house, which was in RCMP jurisdiction, because he'd offered Dunphy too little information about the need for a police call.

Smyth was a member of then-premier Paul Davis's security team. He visited Dunphy alone and unannounced after Davis's staff flagged a single post on Twitter as "of concern."

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 and only child, Meghan, 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."

Lawyers for the Dunphy family and Smyth declined to comment Tuesday as they review the findings.

Dunphy, 58, was an injured worker who often aired his disgust with the workers' compensation system -- and what he saw as political indifference -- on social media. His daughter and close friends testified he was angry but never violent, and was never known to use guns.

The RCMP reported that a loaded .22-calibre rifle, which had belonged to Dunphy's late father, was found near his body. Investigators said no fingerprints could be lifted as the weapon was too old, pitted and rusted.

Barry's report makes a number of recommendations. They include crisis intervention and de-escalation training for all police officers in Newfoundland and Labrador, with mandatory requalification every three years.

Barry recommended serious police-involved incidents be investigated by a civilian-led agency as in other provinces. Parsons has committed to forming such a team.

The commissioner also underscored "material deficiencies" in the RCMP probe of the shooting, saying they "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 said.

RCMP investigators told the inquiry they were perhaps too casual with Smyth, but that it didn't taint their work overall.

One in particular confirmed for Smyth a day after the shooting that Dunphy's unfired rifle was loaded, telling him: "You saved your life."

Smyth was not photographed the day of the shooting, nor was his unmarked police vehicle searched. He was given a private room at the local RCMP detachment to meet with RNC officers and did not give a statement, as per their advice, until a day later so he could regroup. The RCMP did not seize his work cell phone for 19 days.

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

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

"We need to restore public trust in our policing and our justice system. And I think the steps we are taking show that we are dedicated to that," said Parsons.

Smyth was the only witness to the killing. Barry stressed he found no evidence of political influence, despite various theories on social media that Dunphy was targeted for criticizing former Progressive Conservative ministers.

Dunphy's daughter, Meghan, raised concerns early on about the objectivity of the RCMP probe. She filed a lawsuit last spring.

"The death of Donald Dunphy was caused by the wrongful act or neglect of Joseph Smyth," says the unproven statement of claim.

It also names as defendants the Royal Newfoundland Constabulary and the Newfoundland and Labrador government for its role overseeing the force.

The inquiry cost almost $2.9 million.