The Royal Canadian Mounted Police (RCMP) said earlier on Wednesday that Myles Sanderson, 30, was taken into custody near the town of Rosthern, Saskatchewan, about 100 kilometres southwest of the area where the killings occurred on Sunday.
Global News, citing multiple law enforcement sources, reported Sanderson surrendered to police and was taken away alive in an ambulance after a highway pursuit in which police rammed his vehicle off the road.
He died shortly after of injuries authorities believe were self-inflicted.
His older brother and accused accomplice, Damien Sanderson, 31, was himself found slain on Monday, a day after the stabbing rampage, in a grassy area of the James Smith Cree Nation.
Police have said they were investigating whether the younger sibling might have killed his brother, and that Myles may have sustained injuries requiring medical attention.
There was no immediate official word of Myles Sanderson's death from Canadian authorities, who were expected to hold a news conference on Wednesday evening.
"There is no longer a risk to public safety relating to this investigation," the RMCP said in an alert announcing the end of the four-day manhunt.
As well as the 10 victims killed, 18 others were wounded in the rampage, which ranks among the deadliest attacks in Canada's modern history.
Police said some of the victims appeared to have been targeted, while others were apparently random.
Authorities have offered no motive for the attacks, which occurred on the James Smith Cree Nation reserve, home to about 3400 people, and the nearby village of Weldon, about 300km north of the provincial capital of Regina.
Sanderson's arrest came hours after new details about the victims and the circumstances of their deaths were brought to light by relatives.
During an emotional news conference on Wednesday, Saskatoon Tribal Council Chief Mark Arcand revealed his sister, Bonnie Burns, 48, and his 28-year-old nephew, Gregory Burns, were stabbed to death in their front yard on the James Smith Cree reserve between on Sunday morning.
Burns' other three sons and two foster children were home at the time of the attacks.
"She was protecting her son. She was protecting these three little boys. This is why she's a hero. She's a true matriarch," Arcand said of his slain sister.
Dayson Burns, 13, was stabbed in the neck but survived, and another young boy in the home hid behind a high chair watching the violence unfold, Arcand said.
Ten of the wounded remained in hospital as of Tuesday afternoon, with seven in a stable condition and three critical.
Sanderson had been a fugitive since May when he stopped meeting his parole officer after serving time for assault, robbery and other offences, CBC News reported.
