REGINA -- The parents of a six-year-old boy who was beaten to death by an older child while in foster care are suing the Saskatchewan government for negligence.

Lee Bonneau was found with head injuries in a wooded area on the Kahkewistahaw reserve in 2013. He was last seen walking with an older boy outside a recreation complex, while his foster mother was playing bingo.

The province's child advocate said in a report last year that the 10-year-old boy who killed Lee had behavioural issues, shouldn't have been in the community unsupervised and didn't get the help he needed.

School staff, police and community members had repeatedly raised concerns about the older boy's behaviour.

Mounties believed he had broken into a home two years earlier and killed a pregnant dog and her unborn pups. The boy had also been hearing voices.

"He was known as a threat to any young child on the reserve," says the statement of claim filed Thursday in Regina.

"Employees of the defendant arbitrarily and without sufficient justification removed a child from the care of his parents and negligently placed him in a place where he was at risk."

Because he was under 12, Lee's killer could not be charged under the Youth Criminal Justice Act.

Tony Merchant, the lawyer representing David Bonneau and Stacey Merk, said Lee's father tried several times to persuade social workers to return the boy.

Two weeks before his death, Lee told his father in front of a social worker that other boys on the reserve were beating him up and he was scared to go back, says the lawsuit.

"The father particularly agonizes over why he couldn't have done more and why he couldn't succeed with social services in getting the child back to him," said Merchant. "He couldn't get the boy out of their clutches and, while still with them, the boy got killed."

None of the allegations in the lawsuit has been proven in court.

A spokesperson for the government did not return a call for comment.

A coroner in an inquest in April determined there were failures in the system and both boys fell through the cracks to some extent. A jury made 19 recommendations that included improving communication between agencies and revising the size of service centres for rural offices.