EDMONTON, Alberta (AP) — Canadian police said early Sunday that an attack on an officer outside a football game 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 think he acted alone, but are not ruling out that others may be involved.

The chaos began outside a Canadian Football League game on Saturday night when police say a white Chevrolot 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. He said he didn't know the extent of the pedestrian injuries.

Knecht said an Islamic State group flag was found in the front seat of the car and seized as evidence.

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 rolled 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.