According to the Mounties, the Royal Newfoundland Constabulary officer was invited into Dunphy's home when he arrived last weekend in Mitchells Brook, N.L., to investigate what was perceived to be a threat made against the premier and another politician.
A 15-minute conversation occurred when there was a "sudden and dramatic" change in the demeanour of the visit, the RCMP said in a statement Tuesday.
At that point, the RCMP said, Dunphy aimed a long-barrel firearm at the officer.
The RCMP said evidence indicates the RNC officer responded with lethal force. Dunphy died at the scene.
A .22-calibre rifle was found on the floor of Dunphy's home. During a forensic investigation, it was determined the gun was loaded.
According to the RCMP, the RNC officer conducted a routine "risk assessment" before making the trip to Mitchells Brook to investigate the perceived threat made against Davis and MHA Sandy Collins.
However, the officer determined it was a "low-risk" situation and it wasn't necessary to bring along a second officer. The RCMP Holyrood detachment, which polices the rural area, was contacted prior to the visit.
The RCMP said its investigation is ongoing.