GRIMSHAW, Alberta — A school bus driver was killed and more than a dozen students were injured when their bus collided with a semi-truck on Monday morning.

The bus was from Peace River School Division. District officials said in a press release that there were 14 students, ranging from elementary to high school, on the bus.

“The unthinkable happened this morning,” Superintendent Paul Bennett said.

The crash happened on a highway north of Grimshaw, which is near Peace River in northern Alberta.

The Royal Canadian Mounted Police’s preliminary investigation indicated that the school bus crossed the center line before it collided with the truck, the Grand Prairie Daily Herald-Tribune reports. A photo from the scene shows the bus on the side of the road, its front end crumpled.

Bennett said in the district press release that the school bus driver, who was a substitute, “sustained life threatening injuries” in the crash and died that morning.

“Our deepest condolences, thoughts and prayers are with the family during this very difficult time,” the superintendent said.

Six students on the bus sustained minor injuries. Seven students suffered more serious injuries, including broken limbs. One of those students was flown to Edmonton for treatment for “serious but non-life threatening injuries,” Bennett said. Parents were notified per the school district’s emergency response plan.

“We will continue to support our students, staff and families in any way we can,” the superintendent said on Monday. “Students at the affected schools have been notified of the accident, letters are being sent home with parents and counsellors are on-site to provide support for students and staff today and in the coming days.”