The teen, who cannot be identified under Canadian law, was indicted on four counts of first degree, or premeditated murder and seven counts of attempted murder as well as a weapons charge during a brief court appearance yesterday.
A court official told AFP the accused would remain in custody until his next scheduled appearance on February 22.
On Friday, the suspect killed two brothers - Drayden and Dayne Fontaine, aged 13 and 17 - at their home in La Loche, Saskatchewan, before going to a nearby school.
He was arrested after police received an emergency call about "a person discharging a weapon in the community," RCMP superintendent Maureen Levy said.
The attack has traumatized the 3,000 inhabitants of the small lakeside community and shocked Canadians.
Unlike in the United States, mass shootings are rare in Canada, where firearms are more tightly regulated than south of the border.
