Lying on his back on the floor of a prison shower, Matthew Hines uttered what may have been his final words.

"Please, please," he said. "I'm begging you, I'm begging you."

Guards at the Dorchester Penitentiary in New Brunswick turned the water back on.

Thirty seconds later, the water was switched off. The 33-year-old inmate appeared to have a seizure.

He was taken to The Moncton Hospital — a half-hour drive away — where he was pronounced dead.

For the last 13 months, Hines's family in Cape Breton believed what they say they were told by Correctional Service Canada (CSC) — that Hines, who had a history of seizures, had died from a seizure.

Publicly, the federal corrections agency has said little about the May 27, 2015, death. At the time, the agency issued a press release saying Hines was "found in need of medical attention" and staff "immediately" performed CPR.

The family didn't know that some of the details in that press release were wrong until late June, when they got a copy of a 49-page internal board of investigation report about Hines's death.

The report shows that correctional staff were with Hines throughout the incident and prison medical staff did not give him any "treatment."

The cause of death was likely lack of oxygen after being pepper sprayed five times by guards, according to a post-mortem report. (A coroner's final report on the cause of death has yet to be released.)

The full story devastated his family.

"I could not believe what Matthew went through," his older sister, Wendy Gillis, told CBC News.

"It was just horrible."

The final minutes

Hines died in May 2015 and according to a post-mortem report, the cause of death was likely lack of oxygen after being pepper sprayed five times by guards. 2:04

Less than two hours after his struggle with guards began, Hines was dead.

The internal report says the inmate refused to return to his cell at 10:13 p.m. He appeared to be "confused" and was "physically unco-operative," according to the report.

A minute later, prison staff began using force.

One guard struck him with a closed hand twice, while another delivered an open-handed hit to Hines's head and two knee strikes to his right side.

As they restrained Hines on the floor, he was pepper-sprayed once.

Minutes later, 10 correctional officers escorted Hines toward the administrative segregation unit.

The report says even though he was "sufficiently under control of staff," Hines was pepper-sprayed in the face four times by one guard, with only seconds between each burst — a violation of policy.

Officers took him to a decontamination shower to wash off the pepper spray. With his hands in cuffs and his shirt pulled over his head, Hines slipped and fell on his back, hitting his head on the wall.

On a handheld camera video of the struggle between correctional officers and Hines, he can be heard telling guards that he couldn't breathe.

Hines was pronounced dead in hospital at 12:04 a.m.

Fifteen months later, New Brunswick's Office of the Chief Coroner hasn't submitted a final report and has given no indication when it will.

An escalation of force

A struggle between Hines and guards at Dorchester Penitentiary escalated quickly. Documents show Hines was hit by guards when he wouldn't return to his cell.

CSC declined an interview for this story.

In a statement, spokeswoman Lori Halfper said she couldn't discuss details of Hines's death, or any possible disciplinary action against staff, due to privacy legislation.

She said the ongoing investigation into Hines's death has identified areas CSC needs to focus on improving, but she did not provide specifics.

The agency also refused to provide CBC News with copies of videos that show the altercation between Hines and guards, again citing the ongoing investigation into his death.

The videos are referenced frequently in the report, which explains how Hines quickly went from socializing with other inmates to fighting for his life on a shower floor.

The report says guards, who had out-of-date training, used "inappropriate" force on Hines.

Investigators also found that, contrary to the CSC news release on Hines's death, the nurse on duty at the prison failed to "provide Hines with the required medical assessment and treatment."

In total, the redacted copy of the report details at least 12 instances of staff not following policy.

The findings have left the Hines family wondering if anyone will ever be held accountable for what happened.

Undiagnosed mental illness

Before he was taken back to prison, Matthew Hines told his sister that he feared he would die behind bars. He died in custody a month later. (CBC)

Hines's sisters remember him as having a kind heart, the kind of guy who would do anything to get a smile.

"He made friends with everybody he met," MacLeod says.

"If he met a homeless person on the street, he'd bring him home."

As a teenager, he started experimenting with drugs, taking anything he could find on the streets. That behaviour led him to crime.

His sisters believe an undiagnosed mental health condition was at the root of his downward spiral.

At 19, Hines was hospitalized for paranoia and signs of psychosis. But he never received a formal diagnosis.

Hines feared he'd die in prison

His family believes he may have been having a psychotic episode on the night of April 18, 2015, when he woke his parents up to say someone was watching him. He was living at home in Sydney, N.S., after being paroled.

Worried for his safety, his family called 911.

When police arrived, Hines was doing jumping jacks around the house. The police report says he wouldn't calm down, but didn't appear to be "combative or abusive."

His parole was revoked and he was returned to prison to serve the final months of a five-year sentence for bank robbery.

Gillis says she stood with her brother outside on the night he was taken away, not knowing it would be the last time she would see him alive.

Wendy Gillis and Helen MacLeod want justice for their brother who died at the Dorchester Penitentiary. (CBC)

He told her he thought he would die inside prison. Gillis says she assured him that no one would hurt him.

"Little did I know, he wasn't back very long before we got the call," she says.

Justice for Matthew

Hines was set to be released from prison in October 2015.

He planned to go home to Sydney and help take care of his parents.

Instead, they bought three burial plots in Ingonish, N.S., and Hines was buried in the middle one — so his parents can always watch over him.

The Hines family wants changes in the correctional system.

Families, they say, shouldn't have to wait 13 months for basic details about their loved one's death.

They also want better training for guards who have to deal with mentally ill inmates, something the CSC says is a priority. The agency spent $85 million on mental health services in 2014-15.

The family also believes the guard who pepper-sprayed Hines four times in a row should be banned from working in a prison.

"Justice has to be done for Matthew," MacLeod says.

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