Investigators now believe Miles Sanderson was the lone killer in a mass stabbing attack in Canada’s Saskatchewan province in September — and his brother, who was initially named a suspect, was among those he killed, police said Thursday.   

  That means 11 people have been killed — not 10 as previously reported — in the attacks in or near northern Saskatchewan’s James Smith Cree Nation, an indigenous community, the Royal Canadian Mounted Police said Thursday.   

  And it’s a major twist in authorities’ view of Sanderson’s brother, Damien Sanderson, who investigators initially said was a suspect along with Myles Sanderson as police responded to the Sept. 4 stabbings.   

  The murders gripped Canada for days as authorities searched for the couple.  During the manhunt, Damien Sanderson, 31, was found dead on Sept. 5 near a home on the James Smith Cree Nation reservation.  Miles Sanderson, 30, was arrested Sept. 7 after a vehicle pursuit in Saskatchewan and died later that day after suffering “medical distress,” police said.   

  While authorities are still investigating the events leading up to the stabbings, they “believe it is important to clarify Damien’s involvement,” RCMP said Thursday.   

  “After completing 250 interviews, processing more than 670 exhibits, reviewing and following up on more than 100 … calls for service, investigators have determined … Damien Sanderson was the victim of a homicide by Miles Sanderson,” an RCMP statement said.   

  “Miles Sanderson committed all of the murders alone,” the statement said.   

  Police have not said how or when Damien Sanderson died.  On the day his body was found, police said he had injuries not believed to be self-inflicted.   

  Although investigators no longer believe Damien Sanderson killed anyone, they found that “Damien was involved in the initial planning and preparations for the attacks.”   

  “We are still investigating the extent of Damien’s involvement,” the RCMP statement said.   

  Investigators are trying to get “an accurate picture of the motivations behind these crimes and why some of the victims were targeted,” the RCMP said Thursday.   

  “This will take time to complete and the reality is we may never know exactly why,” RCMP said.   

  In addition to the 11 dead, 18 others were injured in a stabbing spree that covered several crime scenes on Sept. 4 in the indigenous community and a nearby rural village, authorities said.   

  In the hours after the attacks, police said both brothers were suspects and that investigators believed they were traveling together in a vehicle.   

  It wasn’t until Sept. 7 — the day Miles Sanderson was arrested and died, and two days after Damien Sanderson was found dead — that a reporter asked RCMP Assistant Commissioner Rhonda Blackmore if Miles Sanderson was the one who committed the murders.   

  “Our evidence that we received indicated that Miles Sanderson was responsible,” although he noted that investigators were still trying to confirm exactly who was involved.   

  In Thursday’s statement, though RCMP said they still did not have a full understanding of the motive, they said both brothers were “involved in at least three violent altercations involving other people on the James Smith Cree Nation” before the killings.   

  “None of these violent altercations were reported to police prior to the commission of the homicides” on Sept. 4, the RCMP said.