Levy said authorities received a call about 1 p.m. Friday saying a weapon had been discharged at La Loche Community School in La Loche. Officers went to the school and at 1:47 p.m. arrested a suspect and seized his weapon.
Earlier reports said five people had been killed and two wounded.
Police were investigating at two sites, the school and a residence in the town, Levy said. The injured were taken to University Hospital in Saskatoon, she said.
Levy revealed few details and wouldn't give the names of the suspect or victims, whether the shooter and victims were students and what kind of weapon was used, saying the integrity of the investigation had to be protected.
Canadian Prime Minister Justin Trudeau earlier addressed the nation, saying, "Obviously this is every parent's worst nightmare" and calling it "a terrible, tragic day."
'Run, bro, run!'
The Star Phoenix newspaper quoted
a student who said he was returning from lunch when shots were fired at the school. He said friends ran past him urging him to get out.
"Run, bro, run!" Noel Desjarlais-Thomas, 16, said his friends told him as they fled. "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."
School coordinator Norma Janvier told the Star Phoenix she was in her office when she heard shots.
"I didn't know what was going on," she said. "I thought the kids were just playing around or something, like a locker slamming and stuff."
She said another teacher stopped her from leaving the office so she waited until someone said it was safe.
"All I heard was cops running around in the school," she said.
'A lot of people are in shock'
Clearwater River Dene Nation Chief Teddy Clark described the shooting as devastating in an interview with The Star Phoenix newspaper.
"Both Clearwater and La Loche, a lot of people are in shock. This is something that you only see on TV most of the time," Clark told the newspaper.
The school provides a prekindergarten to 12th grade education and houses about 900 students in two buildings, the school's Facebook page says. The town has about 2,600 people.
Levy said a lockdown at the school was lifted after several hours.
Royal Canadian Mounted Police and emergency personnel responded to the shooting, according to a Facebook post by Saskatchewan Premier Brad Wall.
"Words cannot express my shock and sorrow at the horrific events today in La Loche," he said. "My thoughts and prayers are with all the victims, their families and friends and all the people of the community."
Saskatchewan Education and Social Services will be providing crisis support and counseling services to the school and the community, the premier said.