Correctional Service Canada has fired one staff member and disciplined three others after an inmate was beaten and repeatedly pepper-sprayed at a New Brunswick prison before his death.

The top correctional official in Atlantic Canada admits there was "staff misconduct" and "excessive force" in the case of Matthew Hines, who died in hospital on May 27, 2015 — less than two hours after his struggle with guards at Dorchester Penitentiary began.

"We take this case very seriously and we're trying to learn from it," Scott Harris, regional deputy commissioner for the Atlantic region, said in an interview.

Matthew Hines died in custody at Dorchester Penitentiary in New Brunswick on May 27, 2015. (CBC)

CBC News has also learned that RCMP have reopened the criminal investigation into Hines's death, after saying last month their investigation was finished and foul play had been ruled out.

But "additional information" has since come to the RCMP's attention, prompting police to "re-examine" the case, according to Const. Hans Ouellette, a spokesman for the New Brunswick RCMP.

He wouldn't say when the investigation was reopened or what kind of new information police received.

In 2015, Hines died in Dorchester Penitentiary. A post-mortem report found pepper spray likely killed him and the RCMP is re-opening its investigation. The CBC's Joan Weeks explains. 8:00

The details of Hines's death were secret until last month, when CBC News revealed the quick escalation of force used against the 33-year-old Cape Breton man after he refused to return to his cell.

Minutes after his struggle with guards began, Hines was hit and then pepper-sprayed five times — including four times in less than one minute.

Death prompted changes

A post-mortem report determined Hines likely died from lack of oxygen caused by the pepper spray.

But correctional officials are still waiting for the final report from New Brunswick's coroner, which could provide a more detailed cause and manner of death. A spokeswoman for the coroner declined to comment on the investigation into Hines's death.

An internal board of investigation report into Hines's death was completed earlier this year and details at least 12 instances of staff not following policy.

It found that guards had out-of-date use-of-force training and used "inappropriate" force against Hines.

Matthew Hines's sisters, Wendy Gillis and Helen MacLeod, want more information about their little brother's 2015 death. (CBC) It also revealed that a nurse on duty failed to "provide Hines with the required medical assessment and treatment," even though he was in medical distress.

Harris listed a number of changes the correctional service has made because of Hines's death, including more training for front-line staff on what to do when inmates are having "paranoid delusions" or other unexpected reactions.

Hines had a history of mental health issues and his family believes he was having a mental health crisis when he appeared "confused" and didn't follow orders to return to his cell.

When asked if further disciplinary action may come, Harris said the correctional service is waiting to see the results of the police and coroner's investigations.

"We will take the necessary action as required based on whatever may come forward," he said.

'It's the last thing we can do for him'

Sixteen months after their baby brother took his final breath, Hines's sisters are tired of waiting for answers.

"It shouldn't take that long to decide how a person passed away," Helen MacLeod said.

They've retained a lawyer, Julie Kirkpatrick, who has written to several public officials, asking them to give the family all the information they have about Hines's death.

That includes a copy of a video filmed by correctional staff just before Hines died.

The family has been dealing with "conflicting and confusing" information from public officials since the day Hines died, Kirkpatrick said.

Scott Harris, Correctional Service Canada's regional deputy commissioner for the Atlantic region, says corrections officials are trying to learn from the death of Matthew Hines. (CBC)

"Matthew was their son and their brother. They are entitled to have the information at their fingertips that others have on their desks," Kirkpatrick said.

She said Harris called on Tuesday and promised to provide an update in the next two weeks about the information they want.

The family is also fighting for a coroner's inquest to be called into Hines's death.

If Hines died inside a prison in Ontario, such an inquest would be mandatory.

But New Brunswick doesn't have legislation requiring an inquest after an in-custody death, leaving it to the discretion of the province's chief coroner.

"It's the last thing that we can do for him," his sister, Wendy Gillis, said. "And we will."

Both sisters said they were relieved when they heard police are revisiting the investigation into their brother's death.

But that doesn't make each day without Hines — remembered for his big smile and love of cooking — any easier.

"You wake up in the morning and you think of Matt," MacLeod said.

"You go to bed at night and you think of Matt and just what he went through. I'm really glad that they're actually opening up and letting us know a few things."

'Staff errors'

In the first interview the correctional service has given about Hines's death, Harris also apologized for a news release that contained false information about the case.

Issued hours after Hines died, it said he was "found" unresponsive by staff, who "immediately" performed CPR on him.

Matthew Hines's family has learned that he may have died from lack of oxygen after being pepper-sprayed by guards five times. (CBC) The board of investigation report shows correctional staff were with Hines throughout the incident and he didn't receive required medical "treatment" until paramedics arrived.

Staff didn't have as much information as they should have had when writing the news release, Harris said.

"We've since determined there were staff errors that were made there, and we do apologize to the family and also to all Canadians for those errors."

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