HALIFAX -- It was almost three years ago that Lionel Desmond -- a deeply disturbed Afghan war veteran diagnosed with PTSD -- bought a rifle and headed to his modest home in rural Nova Scotia.

As night fell on Jan. 3, 2017, the retired 33-year-old corporal entered the house in Upper Big Tracadie and killed his mother, wife and young daughter before taking his own life.

On Monday, relatives, government officials and lawyers will gather in a municipal building in nearby Guysborough, N.S., to begin a fatality inquiry that will try to determine what happened to Desmond and what can be done to prevent similar tragedies.

"Desmond had serious PTSD," said lawyer Adam Rodgers, who represents Desmond's sister Cassandra -- the personal representative of Desmond's estate.

"He tried to get it treated for 10 years in different ways, and none of it quite worked. He never found answers. His family wants to find those answers for him and for others."

Rodgers said the inquiry will begin with opening statements from the commissioner overseeing the inquiry, provincial court Judge Warren Zimmer, followed by statements from various lawyers.

"There were different points where the system failed him," said Rodgers, who practises in New Glasgow, N.S., but grew up in Guysborough. "He was let back into his community without adequate supports and without knowing how he was going to handle that."

The first witness to give evidence is expected to be Nova Scotia's chief medical examiner, Dr. Matt Bowes, the man who reviewed the circumstances of the deaths and recommended that an inquiry be held under the province's Fatality Investigations Act.

The Nova Scotia government promised the inquiry in December 2017.

"Canadians should be paying attention to what's happening in Guysborough, because these issues have not gone away," Rodgers said.

"There are still going to be soldiers going off to combat and coming back with PTSD, coming back to reintegrate with their families and deal with medical and social issues. We want to come up with better ways to deal with those kind of situations. This is something that can affect all parts of the country."

The inquiry will be reminded that on Jan. 3, 2017, Desmond entered his tidy home in nearby Upper Big Tracadie armed with a rifle he had bought earlier that day. Moments later, he shot his wife Shanna, 31, their 10-year-daughter Aaliyah and his 52-year-old mother Brenda -- before turning the gun on himself.

In the months that followed, family members repeatedly said Desmond -- a veteran of two particularly violent tours in Afghanistan in 2007 -- had sought treatment for his mental illness and a post-concussion disorder.

However, they insisted he did not get the help he desperately needed.

Cassandra Desmond, who lost her mother, only brother and his entire family in the murder-suicide, has said she hopes the recommendations from the inquiry will help prevent similar deaths.

She and her twin sister Chantel fought a lengthy, public battle to persuade the government to launch an investigation. They have said Desmond's combat experience in Afghanistan had a profound impact on his personality.

After a medical discharge, he returned home in 2015, a shell of who he used to be. The sisters say his sense of humour had faded, and he seemed in a defensive posture much of the time -- as if he was still in combat.

The inquiry will examine whether Desmond had access to mental health and domestic violence services -- and whether he should have been able to buy a rifle.

As well, the inquiry will investigate whether the health-care and social services providers he dealt with were trained to recognize occupational stress injuries or domestic violence.

And provincial officials will be asked if they faced restrictions when trying to gain access to Desmond's federal health records.

Bowes has said his initial review of the case indicated a lack of co-operation between government agencies, saying the "interconnection between all of those may well have been better."

Among those expected to testify in the coming weeks are representatives for the federal attorney general, who will speak for Health Canada, Veterans Affairs, the RCMP and the federal Public Safety Department.

Nova Scotia's attorney general's office will speak for the involvement of the provincial departments of Justice, Health, Education and Community Services, as well as the Office of African Nova Scotian Affairs and the Advisory Council on the Status of Women.

Zimmer will eventually file a report containing his findings and recommendations. It will not contain any findings of legal responsibility.

Fatality inquiries are rare in Nova Scotia. The last time the government called for such an inquiry was in 2008.

This report by The Canadian Press was first published Nov. 17, 2019.