At a news conference in Regina, Saskatchewan, officials said the boy cannot be prosecuted because he is under 12, The (Regina) Leader-Post reported. They did not identify him or release his exact age.
Lee Allan Bonneau, a 6-year-old who was in foster care, died Aug. 21 after suffering severe head injuries. His caretaker left him outside the Education and Sports Complex on the Kahkewistahaw First Nation reserve in Regina while she played bingo inside.
While Lee was not a member of the tribe, the boy believed to have killed him is, officials said.
"It is a tragedy nobody can be prepared for," Sheldon Taypotat, the chief of the Kahkewistahaw First Nation, said.
Andrea Brittin, an official in the provincial social services ministry, said a treatment plan will be developed.
Staff Sgt. Larry Brost of the Royal Canadian Mounted Police said investigators are sure the boy was the one who injured Lee and caused his death.