Matthew Hines didn't have to die.

That's the conclusion of a scathing report by Canada's prison watchdog, who found that staff at New Brunswick's Dorchester Penitentiary ignored repeated cries for help from the mentally ill man as he was dying.

Hines was beaten and repeatedly pepper sprayed by guards, force that correctional investigator Ivan Zinger deemed unnecessary and inappropriate.

A little more than an hour after the confrontation, Hines was pronounced dead. He was 33.

After his death, Correctional Service Canada ordered the bloodstains to be cleaned, "compromising the preservation of a potential crime scene."

Zinger slams a "flawed and self-serving" investigation by CSC that failed to take into account the gravity of what happened.

"In this case, given the catastrophic breakdown in the staff response it is appropriate to review and question the adequacy and appropriateness of CSC staff investigating and disciplining itself."

Apology

CSC apologized to Hines's family in a statement, admitting, for the first time, that his death may have been preventable.

The agency accepted all 10 recommendations made by Zinger, including that individual managers from CSC should be "held answerable and accountable" for the deficiencies that "directly contributed" to Hines's death.

Other changes include the creation of a team that will conduct disciplinary investigations after use of force results in death or serious bodily injury to an inmate.

CSC also apologized for providing misleading information to the public and Hines's family. 

That includes a press release that said Hines was "found" in need of medical attention and that he received CPR. 

Matthew Hines

Matthew Hines died in custody of the Dorchester Penitentiary on May 27, 2015. (CBC)

"We want to assure Mr. Hines's family and friends, and all Canadians, that CSC takes every death in custody seriously, and we are committed to making sure the important lessons learned from his death are engrained in our response to similar situations in the future," Don Head, commissioner of the Correctional Service of Canada, said in a statement.

In a separate statement, Public Safety Minister Ralph Goodale said he supports Zinger's findings.

Hines was serving a five-year prison sentence for bank robbery when he refused to return to his cell at Dorchester Penitentiary on the night of May 26, 2015. 

Less than two hours later, he was pronounced dead.

During those two hours, Zinger documented 21 instances of staff not following policy.

'Like waterboarding'

That includes a rapid escalation of force, including five bursts of pepper spray to the face. Four of those bursts came in less than a minute, even though Hines appeared to be in control of guards.

"Please, please," Hines said after being pepper sprayed. "I'm begging you, I'm begging you."

Before losing consciousness, Hines lay in a decontamination shower with his shirt pulled over his face.

"In his state, the sensation could conceivably feel like waterboarding," Zinger wrote.

Ivan Zinger

Ivan Zinger, Canada's prison watchdog, has slammed Correctional Service Canada for its investigation into the death of Matthew Hines. (Government of Canada)

Despite Hines's pleas for help and signs of medical distress, the nurse on duty at the prison "failed to conduct any assessments" or perform "life-saving treatment."

That contradicts documentation the nurse filed at the time, the report says. She no longer works with CSC.

The cause of death, according to a post-mortem report, was lack of oxygen due to being pepper sprayed.

But CSC's investigation into Hines's death didn't directly link the "multiple uses of pepper spray to Matthew's ensuing medical emergency," Zinger wrote.

Matthew Hines

Matthew Hines begged for help before taking his final breath at Dorchester Penitentiary. He was pronounced dead on May 27, 2015. (CBC)

Two guards were given reprimand letters, while a correctional manager received a reprimand letter and lost one day's worth of pay.

But no one, Zinger wrote, has been "held to account" for the deficiencies that "contributed to Matthew's death."‚Äč

New Brunswick RCMP re-opened the investigation into Hines's death in the fall of 2016 and transferred the investigation to Nova Scotia RCMP.

On Tuesday, Nova Scotia RCMP said the file has been submitted to New Brunswick's public prosecution service.

Police in New Brunswick typically send a file to the Crown prosecutor's office for review "if the police are satisfied that there is sufficient evidence" to lay a charge, according to the attorney general's pre-screening policy.

The public prosecution service has the final say on whether charges are laid in New Brunswick.

For more than a year, Hines's family in Cape Breton believed their son and brother died from a seizure. The true story of his death continues to haunt them.

Hines struggled with mental health

"The sheer number of correctional staff who were involved in or witnessed Matthew's death is incomprehensible to us," Hines's family said in a statement released on Tuesday.

"Why did no one prevent this from happening to him?"

Hines struggled with mental health issues throughout his life, but couldn't get the help he needed in Cape Breton, his family said. They believe he may have been having a mental health emergency on the night of his death.

Marg Hines, the victim's mother, wants to see more mental health support for inmates like her son. 

When she found out her son died behind bars, it felt like she had a hole in her heart, she said in an exclusive interview with CBC News. She felt like she couldn't breathe, like she too might die.

It's been nearly two years since that day, but Marg Hines remains determined to get justice for her son.

"I'm going to fight so hard," she said.

"Until the people responsible for causing his death are sentenced to prison and see what it's like in there."

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Marg Hines

Matthew's mother, Marg Hines, vows to get justice for her son. (Gary Mansfield/CBC )