People placed candles and flowers in the snow in a makeshift memorial outside the La Loche Community School in Saskatchewan province, where two people were killed and seven were wounded.
A teacher's assistant who was killed was described as "a fantastic person".
Two teenagers were also shot dead by the gunman in a house.
A 17-year-old boy was charged with four counts of first-degree murder and seven counts of attempted murder on Saturday. Police said the male suspect cannot be named under Canada's Youth Criminal Justice Act.
It happened in the Dene aboriginal community of La Loche - the Dene are a First Nation group who inhabit the northern parts of Canada.
Royal Canadian Mounted Police Chief Supt Maureen Levy said the suspect was arrested outside the school.
Marie Janvier, an educational assistant, was identified by her boyfriend Deegan Park as one of those killed at the school.
He said: "She was that much of a great person to turn me right from all the wrongdoings I used to do. She was a fantastic person."
Ashton Lemaigre, a teaching colleague at the school, said Ms Janvier was hoping to get her teaching degree and she was very kind to the children.
"The kids loved having her around," said Ms Lemaigre. "They would just come running to her. And she was just a friend to everybody."
A second victim was identified as Adam Wood, a new teacher at the school.
His family in Ontario said he was an adventurer with a passion for life who made people laugh.
Canadian Prime Minister Justin Trudeau was attending the World Economic Forum in Davos, Switzerland, when he heard the news.
"Obviously, this is every parent's worst nightmare," he said. "The community is reeling."
School shootings are rare in Canada, although one in 1989 at Montreal's Ecole Polytechnique killed 14 women.
US ambassador to Canada Bruce Heyman offered his condolences.
"We have experienced similar tragedies far too often in the United States and understand all too well the heartache and sadness that result," he said.
A remote community in Canada is in mourning after a gunman killed four people on Friday.