LA LOCHE, Sask. -- A young man who was days away from his 18th birthday when he shot up a home and school in northern Saskatchewan, killing four people, is facing a life sentence after a judge ruled Friday that he should be treated as an adult.

Judge Janet McIvor brought down her decision in La Loche, the remote community where the shooting happened in January 2016.

Two teenage brothers were killed in their home before the shooter went to the school where he gunned down a teacher and a teacher's aide. Seven others were injured.

The young man, who is now 20, pleaded guilty in October 2016 to two counts of first-degree murder, two counts of second-degree murder and seven counts of attempted murder.

McIvor said there was evidence that the shooter was at a high risk to reoffend and suggested a youth sentence would not be appropriate because of the shooting's profound impact on the community.

The judge noted the "incredible level of violence" against the teen boys and at the school.

"He ambushed and murdered both of them," McIvor said of brothers Dayne and Drayden Fontaine.

She also said the school shooting was "planned and calculated" and pointed out that the killer had shot teacher Adam Wood twice at close range.

The shooter faces the prospect of life in prison with no chance at parole for at least 10 years. Lawyers are to make submissions on the final sentence March 16. A publication ban remains on the young man's name until at least then.

The defence had argued he should be sentenced as a youth because he suffers from fetal alcohol syndrome and has cognitive problems that have affected his maturity.

"We obviously are disappointed in the result," defence lawyer Darren Kraushaar said outside court Friday. "Our role was to put all the information before the court to help her make a decision. Obviously we are not happy with the decision, but we accept it."

The Crown and many of the victims had asked that the teen be sentenced as an adult.

"This was a very tragic event and we felt that we could make an application for an adult sentence, because there were very compelling reasons for it. We appreciate that the court listened to our submissions," Crown prosecutor Pouria Tabrizi-Reardigan said.

"I hope that the community can have closure at this point."

La Loche Mayor Robert St. Pierre said it is the decision he and many in the community wanted, but it doesn't solve everything.

"We've still got hurt people. We still have people that are ... angry and upset, and it's still what we've got to live with."

There has been very little explanation for the shooter's motive. There were suggestions in the aftermath that the teen had been bullied at school, but he told police that wasn't the case.

He told officers that he regretted shooting the two brothers, that they weren't part of the plan. Asked what his plan was, he responded: "Go to the school and shoot the f---ing kids." Asked who he was targeting, he said: "Nobody."

An agreed statement of facts read during the sentencing hearing detailed the shooter's murderous path from the home to the high school.

The Fontaine brothers had just played video games with the killer the night before. Dayne, 17, pleaded for his life and said, "I don't want to die" before he was shot 11 times, including twice in the head. Drayden, 13, was shot twice in the head after running into the shooter outside the house and being led inside.

The shooter then posted messages online: "Just killed 2 ppl," and "Bout to shoot ip the school."

Surveillance footage captured his frightening walk through the halls, his shotgun raised, as students and staff ran in fear. Wood managed to call 911 before being shot in the torso and then once again while on the ground. He was pronounced dead in hospital.

Teacher's aide Marie Janvier was shot when she ran to get help for a substitute teacher who had been wounded.

When police arrived, the shooter ran into a women's washroom where he put down his weapon and gave himself up.

St. Pierre said he hopes the community can move on.

"The community needs to start looking at ourselves and what we are doing currently and start building on our strengths," the mayor said.

"We do have a lot of strengths in this community. We need to believe that we can do better and we will do better."