The inquiry into the Lionel Desmond killings is expected to begin hearings in September.
Mr. Desmond, an Afghan war veteran who had been diagnosed with post-traumatic stress disorder, killed his family and himself in rural Nova Scotia on Jan. 3, 2017.
Members of his immediate family have long complained he did not get the help he needed from federal and provincial agencies.
Jennifer Stairs, a spokeswoman for the judiciary, said on Wednesday that provincial court Judge Warren Zimmer will begin hearing evidence in September at a renovated former municipal building in Guysborough, N.S.
On May 21, Justice Zimmer will hear applications from anyone interested in participating in the inquiry.
The 33-year-old Mr. Desmond served two tours in Afghanistan in 2007.
In 2017, 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 family’s home in Upper Big Tracadie, N.S.
Among other things, the inquiry will examine whether Mr. Desmond had access to mental-health and domestic-violence services – and whether he should have been able to buy a gun.
It will also look at whether the health-care providers who interacted with him were trained to recognize occupational stress injuries or domestic violence.
No set time has been set aside for the hearings, which will be live-streamed on the internet.
Ms. Stairs said the hearing site will likely have space for only 12 to 16 members of the public. An overflow room has been set up, as well as two family rooms and rooms for counsel and the media.
Justice Zimmer’s report will make findings and recommendations but will not make a finding of legal responsibility.
Cassandra Desmond – who lost her mother, only brother and his entire family – has said she hopes the inquiry will bring lasting change that helps prevent similar deaths.
She and her twin sister, Chantel, fought a lengthy battle advocating for the inquiry.
The sisters have said Mr. Desmond was a radically changed man when he was medically discharged, and returned home in 2015.
They say his outgoing sense of humour had dimmed and, more importantly, he seemed withdrawn and in a defensive posture much of the time – as if he was still in combat mode.