"Evidence indicates the police officer responded to this threat with lethal force by drawing and discharging his service pistol," Sgt. Greg Hicks said Tuesday.
Hicks said a loaded .22-calibre rifle was seized from the home of 59-year-old Don Dunphy in Mitchells Brook, southwest of St. John's, where he died Sunday. It was found on the floor of the small, tree-shrouded residence next to Dunphy's body and will be examined at a forensic lab, he added.
The Mounties have jurisdiction in the area. They are leading the investigation of the death involving an unnamed Royal Newfoundland Constabulary officer who was part of the premier's security team.
Hicks said the officer was advised Friday of a social media comment "which was felt to be of concern as it was believed to be directed towards provincial politicians." The investigator consulted local Mounties and police databases as part of "a routine risk assessment" before visiting Dunphy alone, Hicks said.
"The officer assessed the risk as low, based on all information he received, and as such determined that a multi-officer response was not warranted."
Hicks said the investigator identified himself as police and was invited in by Dunphy. They spoke for about 15 minutes before "there was a sudden and dramatic change in the demeanour of the visit," he said.
"The police officer was faced with Mr. Dunphy holding a long barrel firearm which was pointed at the officer."
That's when the investigator opened fire, killing Dunphy, Hicks said.
People in the tiny Newfoundland community are asking why an officer unknown to Dunphy would go alone to investigate perceived Twitter threats.
"They're shocked and sad and talking about it," said Mayor David Sorensen in an interview. "This shouldn't have ended the way it ended."
He believes the officer should have more thoroughly investigated before confronting Dunphy, a man who was troubled and reclusive, he said.
"You can't put out a campfire with gasoline."
Friends have said Dunphy was severely injured in a heavy equipment accident while working for a contractor several years ago. He aired his frustration with the workers compensation system on call-in radio shows.
He was also a frequent Twitter user, where he described himself as "a crucified injured worker from NL Canada where employers treat (the) injured like criminals."
Sorensen said Dunphy had lived alone for years after the death of his wife and has a grown daughter, "a very nice girl and a hard worker."
Town manager Susan Parrott said her phone has been ringing steadily since Sunday.
"The community has questions," she said from her home in Mount Carmel. "Everyone feels that if both (the RNC and RCMP) had been in, there's a very good chance that things would have been different."
Police have said the officer was working a regular shift when he visited Dunphy.
Davis, a former constable with the Royal Newfoundland Constabulary, said Monday that his staff told police about potentially threatening tweets Friday, but he was not aware of them until after Dunphy was killed.
Dunphy's Twitter feed Friday included posts to the premier's official account and that of Sandy Collins, the provincial minister for child, youth and family services. They referred to God getting politicians who ignored and laughed at the poor before they could enjoy pensions "they didn't deserve."
"I won't mention names this time, 2 prick dead MHAs might have good family members I may hurt."
Parrott said there has been much debate about whether the posts constituted a threat, and whether they were actually aimed at the premier.
"Tweets can be taken in so many ways and yes, some need to be investigated," she said. "A lot of people took it as a joke ... just as a comment."
— With files from Alison Auld in Halifax.
Follow @suebailey on Twitter.