In the hours before she died in Edmonton hospital bed, four-year-old Serenity was so emaciated she appeared alien, even to her own mother. 

"When I went into the room, it didn't even look like my daughter," her mother said. "It wasn't my daughter at all. I don't know how to explain it. I don't know how people can be so cruel.

"I don't know how you could starve a child. I don't understand it."

The little girl died while in a kinship care placement with relatives on a central Alberta reserve, and the case has raised serious questions about the province's child welfare system. 

A review by Alberta's Child and Youth Advocate Del Graff revealed that Serenity's caregivers had been poorly trained, and an investigation of the home had been inadequate. Graf's investigation also found that Serenity and her two older siblings had been left in the care of relatives despite complaints about abuse.

No one had checked on the welfare of the children for 11 months before Serenity's death.

Medical records obtained by CBC News paint an even more troubling picture.

Paperwork from the emergency room shows that Serenity arrived at a central Alberta hospital on Sept. 18, 2014, suffering from a suspected head injury. Her pupils were permanently dilated. She weighed just 18 pounds.

Her body was covered in bruises. There were signs of trauma on her genitals. Her hymen was missing.

She was airlifted to Edmonton's Stollery Children's Hospital, where doctors determined she had suffered a brain injury so severe there was no chance of recovery.

She remained on life support until Sept. 27, 2014.

More than two years later, Alberta's medical examiner has determined the cause of death but has not released that information to the public. CBC News has confirmed the autopsy report was never provided to the office of the child and youth advocate.

"The medical examiner reported to the police a couple of weeks ago that the cause of death is going to remain undetermined," said Serenity's mother, who under provincial child welfare legislation cannot be named in order to protect the identities of her other children.

"Undetermined with all that abuse? Her hymen was missing and I didn't even know that until a couple weeks ago, until I let someone else see the doctor's report. Nobody told me that. Nobody told me that my daughter had been sexually assaulted."

Wildrose calls for emergency debate 

On Monday, Justice Minister Kathleen Ganley said the autopsy report was not released publicly at the request of the RCMP, to avoid prejudicing the investigation. 

"We're not going to do anything that could potentially prejudice an investigation, on a general basis, on all files that's always the position," Ganley said. "So the RCMP has asked us not to release it and we're not releasing it."

A Wildrose motion in the legislature Monday prompted an emergency debate on what the Opposition called "a matter of urgent public importance."

Wildrose Leader Brian Jean said before the debate the little girl's death underlines a stunning failure in the system that Alberta needs to address immediately.

"Our child welfare system failed Serenity, and Albertans are demanding that significant action and steps are taken so this type of tragedy doesn't happen again," Jean said in a statement. "These shocking details laid out for Albertans require action and a debate in the legislature in order to lift the curtain of secrecy surrounding this case and recognize the demand for justice."

'I'm not a bad mom. I've never hurt my kids'

Serenity's mother said she lost custody of her children in September 2010. She told CBC News that domestic abuse and drug use — she drank and smoked marijuana — resulted in her children being removed from the home.  

"I'm not a bad mom," she said through tears. "I've never hurt my kids. I've never laid a hand on them. I never starved my kids. I always had food in my cupboards.

"There was nothing wrong. The only thing wrong was me deciding to be with someone who was abusive, and I haven't even seen him in five years. It's just horrible."

Serenity and her siblings were placed in foster care, where they were thriving, their mother said. Then came a call from her case worker. The children needed to be sent instead to live with relatives on the reserve.

Kinship care is an alternative to foster care. Advocates of the program say it helps children maintain important ties with their birth families and culture. The provincial kinship care program was first announced in 2004. The number of kinship care homes continues to grow, from 373 in 2005 to 802 in 2010.

"After years and years of me doing things and feeling like I had no hope," the young mother said, "she told me that if I didn't put my kids into kinship care then they would be adopted out separately and I would never see them again.

"I was pushed into doing this."

Though hesitant about uprooting her children again, Serenity's mother said she had no reason to suspect her relatives were anything but capable caregivers.  

But in the weeks that followed, she began to notice troubling changes. Her children were losing weight, and were often covered in unexplained bruises.  

'There is going to be justice for my kids'

"Right away, as much as I hate child welfare, I went back to them, and said, 'You have to get my kids out of there.'

"They did nothing. They didn't check up on my kids. They didn't get back to me about how my kids were doing."

She said after she filed several complaints, her relatives and the caseworkers banned her from seeing her own children.

"I was cut out. It was just devastating. I knew something was wrong."

When Serenity arrived at the hospital she was suffering from severe hypothermia. Bruises ran down her back, legs, pelvis and anus. Her caregivers said she had fallen from a tire swing, but a forensic pediatrician determined her injuries were inconsistent with a fall.

ER staff noted the family's demeanour, writing that the caregivers were "emotionless during resuscitation ... zero crying, zero emotion." 

In interviews, Serenity's siblings told a caseworker they were often deprived of food, and were hit with wire hangers and other objects. They said their sister was beaten on multiple occasions for acting up and "stealing" food.

A caseworker determined that the surviving children were being neglected and there was a substantial risk they would be physically injured or sexually abused in the home. 

No charges have  been laid in connection with Serenity's death. Police have said their investigation remains open.

In the more than two years since her daughter's death, Serenity's mother said she has turned her life around. The 28-year-old moved to the East Coast, trained as a chef, regained her sobriety, and finally regained custody of her remaining children.

"I know that I've made my bad choices and I'm paying for them," she said. "And I'll have to pay for them for the rest of my life. But I think they should be accountable too.

"There is going to be justice for my kids. I never stopped fighting for them then, and I'm not going to stop fighting for them now."