The RCMP released more details in its investigation of the deadly Sept. 4 stabbings in James Smith Cree Nation on Thursday.
According to police Myles Sanderson killed all 11 victims in the rampage, including his brother Damien.
Police said Damien was involved in the planning and preparation of the attacks – but didn’t carry out any of the murders.
Eighteen others were injured at James Smith and in the nearby village of Weldon.
Damien Sanderson’s body was found near a crime scene on the First Nation near a crime scene on Sept. 5, while his brother died days later after he went into medical distress in police custody.
The update comes as the Correctional Service of Canada said it has launched an investigation into the statutory release of Myles Sanderson and how officials made the decision.
There has been criticism from community and tribal leaders over Sanderson’s statutory release from prison, in light of a parole board report that showed Sanderson had a nearly two-decade-long criminal record and a propensity for violence when intoxicated.
The Parole Board of Canada document from February said that Myles Sanderson told the board that regular use of drugs and hard alcohol would make him “lose (his) mind” and get angry.
“Your criminal history is very concerning, including the use of violence and weapons-related to your index offences, and your history of domestic violence,” the report said.
The Correctional Service’s Board of Investigation process is guided by requirements set out in the Corrections and Conditional Release Act.
It is an administrative investigation that will thoroughly analyze all of the facts and circumstances, including whether laws, policies and protocols were followed, and identify any recommendations and corrective measures, as needed.
The findings and any recommendations will be made public when the investigation is complete.