TORONTO:  A gunman opened fire at a high school and a second location in an aboriginal community in northern Saskatchewan on Friday, leaving four dead and at least two injured, officials said.

Prime Minister Justin Trudeau said from Davos, Switzerland that a suspect was in custody. Trudeau initially said five died, but police later corrected that to four.

"This is every parent's worst nightmare," he said. "The community is reeling."

"I'm just so sad."

Marie was Janvier's only child. He said he didn't know if the shooter knew his daughter.

Royal Canadian Mounted Police Chief Supt. Maureen Levy said the gunman was arrested outside the school but declined to release details about him.

Levy said she wasn't sure how many suffered injuries. The prime minister earlier described two injuries as critical.

"At the present time there are four individuals deceased," Levy said.

Levy declined to release more details, saying the investigation is in its early stages. She declined to give the sex or ages of the deceased.

A student who was just returning from lunch when shots were fired said his friends ran past him urging him to get out.

"'Run, bro, run!" Noel Desjarlais-Thomas, 16, recalled his friends saying to him as they fled La Loche's junior and senior high school.

"There's a shotgun! There's a shotgun! They were just yelling to me. And then I was hearing those shots, too, so of course I started running."

Shootings at schools or on university campuses are rare in Canada. However, the country's bloodiest shooting occurred Dec. 6, 1989 at Montreal's Ecole Polytechnique, when Marc Lepine entered a college classroom at the engineering school, separated the men from the women, told the men to leave and opened fire, killing 14 women before killing himself.

The grade 7 through 12 La Loche Community School is in the remote Dene aboriginal community of La Loche, Saskatchewan. The school's Facebook page said it would remain on lockdown until the Royal Canadian Police resolve the matter. It asked the public to stay away.

It was unclear how many died at the school.

Saskatchewan Premier Brad Wall earlier confirmed the shooting.

"Words cannot express my shock and sorrow at the horrific events today in La Loche. My thoughts and prayers are with all the victims, their families and friends and all the people of the community," he said in a statement.

US Ambassador to Canada Bruce Heyman offered his condolences in a statement and noted the problem of school shootings in America.

"We have experienced similar tragedies far too often in the United States and understand all too well the heartache and sadness that result from such a horrific event," Heyman said.

The area's representative in parliament, who attended the same school, was setting up a constituency office in the community when the shooting occurred.

"We're fairly shaken up. It's a sad day," said Georgina Jolibois, who was mayor of La Loche until she was elected to Parliament last fall. "My own nieces and nephews were inside the school."

Jolibois said she went to the school and spoke with some of her family members, who were unharmed.

Bobby Cameron, Chief of the Federation of Saskatchewan Indian Nations, said it was the worst tragedy to ever hit the community. The Dene are an aboriginal group who inhabit the northern parts of Canada.

"It's not something you ever imagine happening here. The whole community, province and country has been affected and we will all go into mourning," said Cameron, who attended graduations at the school for the past few years.  "Right now we're just in a state of shock and disbelief."