Canadian police said they were investigating violent attacks in Edmonton on Saturday night as “acts of terrorism” after a man hit a police officer with a car and stabbed him, and later four pedestrians were struck with a second vehicle in a police chase.

Police arrested a suspect who they believe acted alone, though authorities have not ruled out the possibility that he acted with others, Edmonton Police Service Chief Rod Knecht said at a Sunday morning press conference.

The victims were taken to the hospital for treatment and the officer’s condition was not critical, Knecht said. Details on the condition of the other victims were not immediately available.

Prime Minister Justin Trudeau said that federal authorities was working with local police on the case.

“While the investigation continues, early reports indicate that this is another example of the hate that we must remain ever vigilant against,” he said in a statement.

Canada’s Public Safety Minister Ralph Goodale tweeted that Canada “will not be intimidated by terrorist violence.” Canada’s terror threat level remained unchanged at medium, where it has been since late 2014.

Police said the suspect, believed to be 30, crashed the car through a barricade and hit the officer at about 8:15 p.m. local time, sending him flying 15 feet into the air and against a police cruiser. The suspect then jumped out of the car, stabbed him and fled the scene on foot, police said.

Later that evening, police at a checkpoint identified a man driving a U-Haul vehicle as the owner of the Malibu.

The suspect fled the scene and deliberately attempted to hit pedestrians as police pursued him through downtown Edmonton, sending at least four people to the hospital with injuries, Knecht said.

Police arrested the suspect after the vehicle flipped over during the pursuit.

“We ask that our citizens remain vigilant and observant of their surroundings, and contact police should they notice any other unusual activities around the city,” police said in the statement.

Canada has not experienced as much violence from extremist attacks as the United States and Western European nations, though there have been several deadly incidents in recent years.

In January, a French-Canadian university student was charged with murder after six people were shot and killed inside a Quebec City mosque, in what the Canadian Prime Minister called “a terrorist attack.”

In August 2016, Canadian police raided an Ontario home and killed a man whom they said was a supporter of Islamic State. Police said the man, Aaron Driver, was in the final stages of preparing an attack on a Canadian city with a homemade bomb.

In 2014, Canada was stunned by two deadly attacks that police said were the work of homegrown radicals and led to tougher new anti-terrorism measures.

A gunman killed a soldier at Ottawa’s national war memorial before launching an attack on the Canadian Parliament in October 2014 while, in the same week, a man ran down two soldiers in Quebec, killing one.