HALIFAX -- There will be a joint federal-provincial inquiry or review into the mass killing in April that claimed 22 lives in rural Nova Scotia, but the exact form of that investigation is still taking shape, the province's justice minister says.

Mark Furey said the probe must have certain features, including judicial leadership, the power to compel witnesses to testify and the ability to make binding recommendations.

"We are trying to find a mechanism that will hold agencies accountable," Furey said in an interview. "I just want to make sure we are picking the right one."

Furey said he and his staff are negotiating with Ottawa to determine the best option, which could include a traditional federal-provincial public inquiry led by an independent commissioner.

Since the April 18-19 shooting rampage in northern and central Nova Scotia, the federal and provincial governments have faced increasing pressure to call an inquiry into one of the worst mass killings in Canadian history. Those calling for an inquiry include opposition politicians and more than 30 Dalhousie University law professors.

Last month, the professors said Nova Scotia should establish an independent provincial inquiry, but Premier Stephen McNeil has said he wants Ottawa to lead the process.

One of those law professors, Richard Devlin, said a provincial inquiry would be preferable to a federal or joint federal-provincial inquiry.

"If it just becomes constituted primarily as a federal inquiry, in which the government of Nova Scotia only plays a secondary role, it will be unduly narrow -- relating only to the federal agencies potentially involved," Devlin said in an interview Wednesday.

"I think that the danger is that we will not get the comprehensive inquiry that this tragedy calls for."

Some victims' relatives have also been calling for an inquiry.

On Monday, the daughter of Heather O'Brien -- a nurse who was killed by the gunman on April 19 -- urged the federal and Nova Scotia governments to work together.

In an open letter, Darcy Dobson said "the back and forth about who's responsible for an inquiry is unreal," and argued that "the amount of information being kept from us is deplorable."

Furey said he had read Dobson's letter.

"I want to assure Ms. Dobson and other family members that we continue in regular discussions with the federal government," he said. "But we absolutely have to have the right mechanism and we need terms of reference that are broad in scope and can address of those questions that families and communities have."

The minister, who is also a former Mountie, said the investigation could include an independent review similar to the one the RCMP conducted after three Mounties were killed and two others wounded by a gunman in Moncton, N.B., in June 2014.

That internal investigation, led by a retired RCMP assistant commissioner, focused on the force's response, training, equipment and procedures. There were no public hearings, but the reviewer's final report was released to the public with recommendations.

Devlin said an RCMP review would be too limited in scope since it would focus only on the police force.

"That is not a replacement for a public inquiry. There's no confidence in the public that that would be independent. There's no confidence in the public that will be impartial. There's no confidence in the public that that would be transparent."

Devlin said there are important, broader issues to examine, including the role of intimate partner violence.

The Mounties have confirmed the killer attacked his common law partner before he started killing people he knew and others at random on the night of April 18. Other witnesses have come forward to say they knew about the shooter's history of domestic abuse.

"I think there's increasing consensus that the challenge here is much larger than (the RCMP)," Devlin said. "We should not be thinking about narrowing our focus.... That would be a disservice to the people of Nova Scotia."

As well, Devlin said the minister should refrain from using vague terminology.

"I would really like to hear the minister use the language of a public inquiry and not some vague terms, such as an 'instrument' or a 'mechanism' that has no real sort of precedent history," the professor said.

Furey said he would like the investigation to take a restorative approach, which is what the province did in 2015 when it looked into allegations of long-term abuse at a former orphanage in the Halifax area.

The Nova Scotia Home for Colored Children Restorative Inquiry was not a provincial inquiry in the traditional sense, though it was established under the authority of the province's Public Inquiries Act.

Its collaborative approach featured "sharing circles" with former residents, black youth and community organizations. Instead of providing a list or recommendations, the inquiry's final report offered a "road map" for breaking down what it described as the government's fragmented approach to helping people in need.

"I believe there is an opportunity for some kind of restorative lens that ... facilitates participation and gets the families and communities the engagement they need and the answers they need," Furey said.

This report by The Canadian Press was first published June 3, 2020.