GUYSBOROUGH, N.S. -- Only two hours before Lionel Desmond used a rifle to kill three members of his family and himself, the former soldier appeared coherent and focused when he purchased the weapon at a sporting goods store in eastern Nova Scotia.

The fatality inquiry investigating the deaths, which completed its seventh day of hearings on Wednesday, was shown a silent, 20-minute surveillance video recorded inside Leaves and Limbs Sports in Antigonish around 4 p.m. on Jan 3, 2017.

"He appeared to be calm and composed," said Dr. Faisal Rahman, a senior psychiatrist at St. Martha's Regional Hospital in Antigonish, upon seeing the video.

Two hours later, the mentally ill retired corporal killed his mother, wife and 10-year-old daughter with a rifle inside the family's home in nearby Upper Big Tracadie.

The commissioner overseeing the inquiry, provincial court judge Warren Zimmer, asked for the video to be shown because he wanted Rahman to assess Desmond's demeanour and actions, saying he was looking for any signs of psychosis or agitation.

Rahman is a key figure in the inquiry because he conducted a clinical evaluation of Desmond when he arrived at the hospital on Jan. 1, 2017 -- two days before the killings -- complaining he was distressed after arguing with his wife Shanna the night before.

Earlier this week, Rahman testified that Desmond was pleasant, forthcoming, composed and showed no signs of psychosis or thoughts of suicide or homicide during a 30- to 40-minute interview.

However, he said Desmond admitted the argument was part of a long-standing pattern of conflict with his wife, which had included calls to police in the past. As well, Rahman said Desmond revealed he had struck a table and startled his daughter, but he denied abusing his spouse.

Rahman said he was also aware that Desmond had been diagnosed with PTSD in 2011 after he served in the army during a particularly violent stage of the war in Afghanistan in 2007.

Desmond spent the night at the hospital, mainly because his wife told him he should not come home and he had nowhere else to go, Rahman said. The 33-year-old former infantryman left the hospital the next day and returned on Jan. 3, 2017 -- the same day as the killings -- to make an appointment with another psychiatrist.

When Rahman was asked to explain how an otherwise calm, coherent and forward-thinking man could suddenly transform into a murderer, the psychiatrist said it was clear Desmond's "status" had changed during the intervening period.

But it was clear from the video that Desmond's outward disposition had not changed by the time he reached the sporting goods shop.

"He appeared to be engaged with the business owner," said Rahman. "He was able to concentrate ... and he was decisive ... when browsing and looking around."

However, Rahman said the expression on Desmond's face appeared to be "relatively flat" compared with the rather animated expressions he used during their talk two days earlier.

Tara Miller, the lawyer representing Desmond's family, told the inquiry that Rahman was not aware of certain things about Desmond as the two men spoke at the hospital, and she said the doctor faced some barriers getting information about his patient.

"We know that, based on your interview with Lionel, it appears he either under-reported on incorrectly reported things to you," Miller told the inquiry.

She said Desmond did not disclose he had used his cellphone on Jan. 1, 2017, to conduct extensive research about firearms, and that he had a valid firearms licence.

As well, Desmond had insisted he was not having any suicidal thoughts, but that was in contrast to a report from a Veterans Affairs counsellor who found Desmond had recently experienced "frequent suicidal ideation."

Rahman said getting medical documents from the federal Veterans Affairs Department was difficult.

Miller also noted that Rahman wanted to speak to Desmond's wife that night, but there was nothing he could do when Desmond said he didn't want that to happen. Rahman said privacy legislation prevented him from reaching out to her, adding that he couldn't override the law unless her safety was at risk.

"In his case, according to my assessment, the safety aspect did not trump his personal health information (rights)," he said.

Rahman was also unaware that Desmond had sent several texts to his wife while he was at the hospital, one of which said: "I'm sorry I put my hands on you, I would never hit you."

Miller asked if that comment would have raised concerns about possible domestic violence, and Rahman agreed.

Part of the inquiry's mandate is to determine if the health-care providers who interacted with Desmond were adequately trained to recognize the signs of intimate partner abuse. As well, it will look into how Desmond was able to obtain a firearm.

-- By Michael MacDonald in Halifax

This report by The Canadian Press was first published Feb. 5, 2020.