Photo: The Canadian Press. All rights reserved.

Rescue workers help an injured child after a minivan crashed into a school in St.Paul, Alta., Thursday, Oct.25, 2012. Police say a child was pinned under the minivan after it went through the wall of Racette Junior High School in St. Paul, east of Edmonton.THE CANADIAN PRESS/St.Paul Journal-Ryan McCracken.

When 14-year-old Simon Chamberland saw several Grade 6 students running down the school hallway, crying and screaming with blood dripping down their faces, he thought a gunman was on the loose.

He next heard a panicked secretary at Racette Junior High School announce over the intercom that the building was in lockdown mode. All the teens in his gym class ran for the girls' change room and hid in the corner of the showers.

"I was thinking, 'Oh my gosh, I hope everyone's all right and everyone's safe.'"

Only later did Chamberland realize the chaos Thursday morning was caused by a minivan that had crashed through an outside wall and into a classroom.

Mounties said three students were pinned under the van at the Catholic school in St. Paul. They were airlifted to a hospital in Edmonton, 200 kilometres to the west, with critical injuries.

Health officials said one of the wounded is an 11-year-old girl. Five others were transported by ambulance to the local hospital, but they were released later in the day.

Parent Michelle de Moissac said her 13-year-old daughter sent her a text message at about 9:30 a.m., saying there had been a crash and the school was locked down.

Confused, de Moissac rushed to the school and saw a giant hole in the side of the building. There were ambulance, police and fire crews and a line up of school buses.

She said a teacher told her the van had been driving erratically. It nearly hit a pedestrian a few blocks away before it went down an alley by the school, veered off the road, smashed through a chain-link fence and then went through the building, she said.

The van dove down into the classroom, which sits below ground. There were about 15 students in the Grade 6 French class at the time, de Moissac said.

"Everyone was being taken out by ambulance."

RCMP said the van's driver, a 46-year-old man from St. Paul, received minor injuries and was taken into custody. Photos from the scene show him being led away in handcuffs.