LA LOCHE, Sask. -- As phone calls started coming in from panicked students and teachers about a shooter on the loose, RCMP sped down the street to the local high school and found its main doors blasted with holes.

Mounties say one officer quickly spotted a boy with a gun inside and chased him through the building. Within a few minutes, and without a fight, police say he surrendered.

But so much damage had already been done.

Saskatchewan RCMP say that during the eight minutes the teen was in the La Loche Community school on Friday afternoon, he shot nine people. Two staff members died.

Then they learned there were more victims.

Two brothers, one 13 and the other 17, were discovered dead in a home not far away.

On Saturday, RCMP announced that they had charged a 17-year-old suspect with four counts of first-degree murder, seven counts of attempted murder and unauthorized possession of a firearm.

He can't be named under the Youth Criminal Justice Act.

Investigators could provide no motive.

"It's a significant event for Canada," RCMP Supt. Grant St. Germaine told reporters gathered in the remote Dene community. "I think it's part of changing times. What we're seeing is what appears to be more violence -- and not being able to account for why."

St. Germaine said he also doesn't know if the victims were sought out or targeted at random.

Maria Janvier, 21, died at the school. She had graduated from there two years earlier and was hired as a teacher's aide last fall, said friend Ashton Lemaigre.

She was kind and patient with children and talked about going to university to become a teacher.

Her boyfriend, Deegan Park, said he would have given up the rest of his life just to spend another year with her.

"I grew up not a good guy, but she turned me right," Park said. "I loved her."

Adam Wood, 35, had also just started work at the school in September as a teacher. RCMP said he died of his wounds shortly after arriving at the La Loche hospital.

"Adam was quite an adventurer, had a passion for life, and would often make you laugh until your stomach hurt," said a statement released by his family in Ontario.

Drayden Fontaine, 13, and Dayne Fontaine, 17, were found dead in the house. Their mother wrote on Facebook that she was devastated.

"My heart shattered into a million pieces," said Alicia Fontaine. "So sad I don't have no more babies."

Brittney Lemaigre described her friend Dayne as a funny and caring guy with "a heart of gold."

RCMP didn't release details on whether the seven injured were staff or students. They said four were flown to a Saskatoon hospital and the remaining were to be transported out later when snowy weather conditions improved.

Students recalled a terrifying scene as they fled for their lives when gunfire first erupted in the school. Some said they ran for the doors when they saw a shotgun, while others hid in gym dressing rooms for hours.

One 16-year-old student forwarded to The Canadian Press a screenshot of a chilling exchange that took place on social media just before the shooting.

"Just killed 2 ppl," a young man wrote to his friends. "Bout to shoot ip the school."

The student with the screenshot later posted on Facebook that the shooting happened because the suspect, normally quiet, "was mad."

"This wasn't supposed to happen like this," he said, noting his favourite teacher had been killed.

Saskatchewan Premier Brad Wall said every student and teacher should feel safe going to school. He planned to visit the community Sunday to ensure it has enough resources, including counselling.

Acting mayor Kevin Janvier said the tragedy has hurt everyone in La Loche.

"Hearts have been broken, our faith has been shaken and lost today," he said. "As we move forward together, we will be doing so in an effort to heal as a community."

-- With files from Chris Purdy in Edmonton, Laura Kane in Vancouver and The Associated Press