ST. JOHN'S, N.L. -- The Newfoundland police officer who killed Don Dunphy in 2015 says the day before he went to Dunphy's home alone he spent an hour going through a year of his frequent Twitter commentary.

Const. Joe Smyth visited Dunphy's house in Mitchell's Brook on St. Mary's Bay after staff in then-premier Paul Davis's office flagged, out of context, a single Twitter post he'd made.

The Royal Newfoundland Constabulary officer on Monday told the public inquiry into the killing that he did a "cursory background check" to assess any risk before heading to the address in RCMP jurisdiction.

The decision to go alone wasn't unusual, said Smyth, who was then a member of the premier's security detail. He'd made similar calls alone before, basing the decision on staff resources, risk, "and the impact of a multiple-officer interview on that particular person."

Smyth wrapped his testimony for the day without speaking directly of the events of Easter Sunday 2015. He is scheduled to appear through Wednesday.

Smyth has told RCMP investigators he shot Dunphy once in the left chest and twice in the head after Dunphy suddenly aimed a rifle at him from the side of his chair.

Smyth confirmed to the inquiry that he had met two of the main RCMP investigators several times in the course of his work.

In his testimony Monday, Smyth, 38, also acknowledged being disciplined for a 2005 incident while on a Caribbean vacation. At the time, he'd been an RNC officer for about three years.

Smyth told the inquiry two men robbed his wallet and police badge after a night of drinking in the British Virgin Islands. He said he was "very intoxicated" but tried to go after them.

"Out of frustration I damaged what I thought was an abandoned school bus," said Smyth, who reported the incident to local police.

Commission co-counsel Sandra Chaytor referred to other witnesses who said that, in fact, Smyth damaged several vehicles and was heard screaming that he would kill the men.

"I don't recall saying I was going to kill anybody, no," Smyth said.

Chaytor asked if Smyth downplayed the incident at the time, citing a quote from Smyth to the effect that he should not have been arrested. Smyth said he did not do so intentionally.

"I was under a lot of stress at the time," Smyth told the inquiry.

Smyth said he was disciplined by the RNC for conduct unbecoming a police officer, temporarily suspended and paid about $30,000 in fines.

Smyth also said he was charged with theft when he was 17 or 18.

He stressed that if the Caribbean incident was going to be used to define his character, then equal weight should be given to his police commendations.

For example, he was given a lifesaver award two months before Dunphy was killed. Smyth had used the Heimlich manoeuvre to save a young person choking at a Special Olympics event.

Prior to Dunphy's death, Smyth said, he had drawn his gun about six times, and only once pointed it at someone -- a young man with a shotgun in the midst of a mental health crisis. He did not fire.

Smyth said he took several months of stress leave in 2015 after the Dunphy shooting, but otherwise had no mental health issues.

Smyth had served on the premier's protective unit for about four years before the killing, and had no major use-of-force incidents in that role before April 2015, he said.

Chaytor took Smyth through three use-of-force reports filed within six months in 2007 when he was a patrol officer.

They included a call near the former Newfoundland School for the Deaf, where the inquiry is now being held. Chaytor described Smyth yelling at a male suspect who did not respond and resisted attempts to control him before Smyth punched him in the face.

It turned out the man could not hear, Chaytor told the inquiry.

Smyth said, given that he received no feedback from supervisors, all three instances were reasonable use of force.

"I understand it to be fairly normal," he said of that number. "It's situational."

In the months before his confrontation with Dunphy, Smyth had repeatedly written emails to Davis's inner circle. They noted his concerns about "radicalized" individuals following attacks in Ontario and Quebec, and suggested Davis, as a former RNC constable, could be at heightened risk.

He also raised concerns that disgruntled people affected by a worsening economy could pose security issues.

Smyth said, however, that he did not put Dunphy in such categories. In fact, knowing what he knows about him now, Smyth said he believes Dunphy had much to live for.

An RCMP probe found Smyth's use of force was appropriate and no charges were warranted. He now works in traffic operations.

Inquiry Commissioner Leo Barry will hear from more than 50 witnesses over the next two months about what happened and why. He will not make findings of criminal or civil responsibility but any new evidence could be investigated by police.