ALBERTA, Canada -- Canadian police said early Sunday that an attack on an officer outside a football game with a car and knife and a high-speed chase of a U-Haul that left four people injured in the western city of Edmonton, Alberta, are being investigated as acts of terrorism.
Edmonton Police Chief Rod Knecht said that officers have one person in custody and they think he acted alone. Knecht said an Islamic State group flag was found in the car that hit the officer.
The attack began outside a Canadian Football League game outside Commonwealth Stadium on Saturday night when police say a white Chevrolet Malibu rammed a traffic control barricade and sent an officer flying into the air 15 feet.
Knecht said the driver, believed to be 30 years old, then got out and attacked the officer with a knife before fleeing on foot.
The officer was taken to a hospital and treated for non-life threatening injuries while a manhunt was launched. "It's not critical," Knecht said of the injuries.
A few hours later, a U-Haul van was stopped at an impaired driving check stop north of downtown on Wayne Gretzky Drive. Knecht said the name of the driver was close to the name of the registered owner of the car that hit the officer.
He said the U-Haul then sped off toward downtown with police in pursuit.
Police say the U-Haul intentionally swerved at pedestrians at crosswalks throughout the chase. Four people were injured by the van, but the extent of their injuries was not immediately known.
The van eventually flipped near a downtown hotel and a suspect was arrested. Knecht said the man was known to police, but did not release his name.
"It is believed at this time that these two incidents are related," he said. "It was determined that these incidents are being investigated as acts of terrorism."
Knecht said Edmonton police are working with the Royal Canadian Mounted Police's National Security Enforcement Team and other Canadian security agencies.
Knecht said they didn't call off the chase of the U-Haul due to the seriousness of the crime.
Alberta Premier Rachel Notley said on Twitter that her thoughts are with the injured officer and she's hoping for a speedy recovery.
The Associated Press contributed to this report.