An RCMP investigator says a 10-year-old boy who killed a younger child on a southern Saskatchewan reserve had a troubled childhood that included 28 interactions with police.

Cpl. Donna Zawislak testified Monday at a coroner's inquest into the death of six-year-old Lee Bonneau, who 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 the reserve's recreation complex while his foster mother was playing bingo.

Zawislak told the inquest that the 10-year-old was the subject of complaints including inappropriate sexual behaviour, animal cruelty and break and enters.

"(He) was touching people inappropriately on the school bus. He was dropping his pants."

He also witnessed a theft and a "gruesome" aggravated assault in which a man kicked another man in the face with steel-toed boots, she said.

Saskatchewan's children's advocate determined the boy, whose name is under a publication ban, had behavioural issues and probably shouldn't have been in the community unsupervised.

He could not be charged under the Youth Criminal Justice Act because he was under 12.

Zawislak said the boy's first interaction with police occurred when he was three years old. His father assaulted his mother who ended up in hospital, she said.

Mounties also believe the boy was involved in a break and enter in May 2011 where a pregnant dog and her unborn pups were killed. Zawislak said a baseball bat and golf club were found near the dead dogs and there was blood throughout the house.

She added that authorities worried the boy was "falling through the cracks."

Zawislak testified that the boy's father was convicted of assaulting him and told police he slapped the child in August 2012.

In a report released last year, children's advocate Bob Pringle said the boy didn't receive the help he needed.

He said his investigation found nine child protection concerns reported to the Yorkton Tribal Council Child and Family Services, but as far as his office could determine, two concerns were never investigated. Other investigations were delayed by months.