A 17-year-old is facing four counts of first-degree murder following a mass shooting in an indigenous community in northern Canada.
The teen, whose identity cannot be revealed under Canada's youth justice system, is also facing seven counts of attempted murder and one count of unauthorised possession of a firearm, officials with the Royal Canadian Mounted Police (RCMP) said Saturday.
Friday's shooting rampage in La Loche, in northern Saskatchewan, could be one of the worst school shootings in Canadian history, RCMP Superintendent Grant St Germaine told reporters Saturday.
"The days and weeks are going to be difficult as we come to terms with the impact of what has happened in our community," St Germaine said. "It's a sad and difficult time and no words will take away the pain and sorrow of what has happened."
The victims have been identified as two teachers, Marie Janvier, 21, and Adam Wood, 35, and brothers Dayne and Drayden Fontaine, aged 17 and 13 respectively.
Seven others were wounded in the violence Friday in La Loche, a Dene First Nations community with a population of about 3,000, about 860 kilometres north-west of provincial capital Regina.
The suspect is expected to make his first court appearance next week.
St Germaine said that authorities received calls from teachers and students at the La Loche Community School on Friday at 1 pm (1900 GMT) about a gunman "discharging a firearm at people in the school."
Police tracked down the suspect and pursued him through the school, eventually taking him into custody at around 1:15 pm. No one was injured during the arrest, St Germaine said.
Police then went to a home a couple of blocks away, where the Fontaine brothers were found dead.
Police cordoned off both locations on Saturday, as specialized investigators gather evidence.
St Germaine said police are not aware of any motive at this time.
"Every individual in La Loche has been wounded by this event," said acting mayor Kevin Janvier. "These emotional and mental wounds... will take years to heal.
"The most sorrowing and disastrous event has happened here, in the place where people should have felt safest, in our schools."
Canada has strict gun laws that restrict the sale and possession of firearms to individuals who undergo thorough police background checks and have to follow a special safety course.
However, guns are more prevalent in northern and rural communities where people use them for hunting and protection from predators.
The worst school shooting in Canadian history happened on December 6, 1989 in Montreal's Ecole Polytechnique engineering school, where a gunman killed 14 female students and a university employee, and injured another 13 women, before taking his own life.
The Ecole Polytechnique massacre prompted the federal government to significantly restrict Canada's gun laws, especially, the sale of semi-automatic weapons and military-style assault rifles with large capacity magazines.