EDMONTON, Canada -- Canadian authorities say two incidents in Edmonton are being investigated as acts of terrorism after a man struck a police officer with a car before stabbing him and later plowed a truck into pedestrians on a busy street, injuring at least four people.
A suspect, who has not been identified, is in custody, said Chief Rod Knecht of the Edmonton Police Service in an early Sunday news conference.
Knecht said authorities believe the man acted alone, but haven't ruled out the possibility that others might be involved.
The first incident happened Saturday at 8:15 p.m. (10:15 p.m. ET) when the driver of a white Chevrolet Malibu drove it into a traffic barricade. Police had set up the roadblock near Commonwealth Stadium for an Edmonton Eskimos football game.
A man drove the car at high speed, striking the police officer who had been standing between a traffic barricade and his cruiser.
"The vehicle struck the police officer, sending him flying into the air 15 feet, before colliding with the police officer's cruiser again at a high rate of speed," Knecht said.
The driver jumped out of the vehicle, attacked and stabbed the officer several times with a knife and fled on foot, Knecht said.
There was an ISIS flag in the car, which has been seized as evidence, the police chief said.
The wounded officer was taken to a hospital. His injuries are not critical, Knecht said.
After that incident, police broadcast the name of the Chevrolet's registered owner to patrol officers in the city.
Just before midnight, a police officer stopped a U-Haul truck at a checkpoint and recognized the driver's name as similar to that of the Chevrolet's registered owner. The U-Haul truck then sped off towards downtown Edmonton with police chasing it.
The U-Haul traveled on busy Jasper Avenue, which late Saturday night and early Sunday morning was full of football fans and bargoers, CBC. During the chase, the truck deliberately attempted to hit pedestrians in crosswalks and alleys in two areas along Jasper Avenue, Knecht said.
At least four pedestrians were injured. Their conditions were not immediately known, the police chief said.
The truck eventually flipped, ending the chase. Pictures in the Canadian media showed the U-Haul on its side with the front window shattered. Police are expected to hold a news conference at 3 p.m. Sunday.
In a press conference Sunday afternoon, Edmonton Mayor Don Iveson urged residents to remain calm.
"To the best of our knowledge," he told reporters, "this was a lone wolf attack." He added the suspect was taken into custody and being interviewed by police.
"The Government of Canada and Canadians stand with the people of Edmonton after the terrorist attack on Saturday that sent an Edmonton Police Service officer to (the) hospital and injured a number of innocent people who were out to cheer on their football team and to enjoy an evening in their city," said Canadian Prime Minister Justin Trudeau in a statement Sunday.
"We cannot -- and will not -- let violent extremism take root in our communities," he added. "We know that Canada's strength comes from our diversity, and we will not be cowed by those who seek to divide us or promote fear."