Quebec: A small aboriginal community in western Canada was in mourning on Saturday after a high school student shot dead two brothers and two trainee teachers and left several others wounded.
Friday`s shooting occurred at a home and then at a nearby school in remote La Loche, in Saskatchewan province, Canadian police and other sources said.
Prime Minister Justin Trudeau called it "every parent`s worst nightmare."
Unlike in the United States, mass shootings are rare in Canada, where firearms are more regulated than south of the border.
The suspected shooter, who has not been named, was taken into custody after police received an emergency call about "a person discharging a weapon in the community," RCMP superintendent Maureen Levy told reporters.
Witnesses said the shooter had a shotgun and the acting mayor of La Loche, Kevin Janvier, told CTV News that the alleged gunman was a young man under 21 and a student at the school.
He was being questioned on Saturday. Investigators were pursuing their probe both at the school and at a nearby residence.
Candles burned all night outside La Loche Community School and on Friday night, hundreds of people held a vigil in memory of the victims.
Authorities were yet to name all the dead and the exact number of wounded, but the two brothers were killed at their home, followed by the teachers at the school.
The families of the two young teachers, identified as 23-year-old Marie Janvier and Adam Wood, paid emotional tribute.
"My cousin Marie was among those murdered in La Loche today. She was a charming, sweet young woman and I loved her so much," Patrick Wagenaar wrote on Facebook.
"My thoughts go out to my family and those affected by this tragedy. I`m so sorry."
Wood`s family issued a statement saying: "Adam had just begun his teaching career in La Loche last September and was enjoying his time.
"Adam was quite an adventurer, had a passion for life, and would often make you laugh until your stomach hurt."
In Australia, Canadian tennis player Milos Raonic dedicated his Australian Open win to the victims.
"Today`s victory was for that community and a quick recovery. All of Canada, and I`m sure the world, is behind you," an emotional Raonic told the crowd.Located deep in Canada`s northern boreal forest, 600 kilometers (375 miles) north of Saskatoon, La Loche has about 3,000 inhabitants.
Because it is so isolated, authorities had to send in police reinforcements and dispatch a medical helicopter to airlift some victims to a hospital.
La Loche students said they heard six or seven shots ring out at around 1:00 pm (1900 GMT).
Pupils described how they fled, terrified for their lives.
One boy, 13, told the Toronto Star how he watched his teacher shot dead in front of him.
The teenager was in math class when he heard several shots ring out.
"I got scared and I got down to, like, behind the desk," he said.
The teacher told students to go against the wall, but as the children obeyed, someone fired into the classroom and hit the tutor in the back.
Trudeau was in Davos, Switzerland, where he was attending the World Economic Forum, at the time of the shooting.
The new prime minister said his Liberal government would have to reflect on Canada`s current gun laws in the coming weeks and months in light of the shooting.
The previous Tory government had scrapped a short-lived national registry of rifles and shotguns.
Many Canadians living in rural areas own long guns like the one that appears to have been used in the shooting, and led a strong opposition to the registry they said wrongly targeted farmers and hunters.