EDMONTON, Alberta — A car and knife attack on a police officer outside a football game and a high-speed chase that left four people injured was the work of a single suspected terrorist, a Somalia refugee who was known to police, Canadian authorities said Sunday.

Marlin Degrand, assistant commissioner of the Royal Canadian Mounted Police, said officers took a 30-year-old man into custody. Police declined to identify the man because he had not yet been charged, but said pending charges include terrorism and attempted murder.

Edmonton Police Chief Rod Knecht said an Islamic State group flag was found in the car that hit the officer, and Canadian Prime Minister Justin Trudeau called it a terror attack.

Degrand said the suspect was flagged in 2015 for extremist ideologies and police interviewed him at the time, but he said charges were not warranted after an “exhaustive investigation.”

By The Associated Press