Ten people were killed and 15 others injured after a driver plowed his white rented van into a lunch-hour crowd on a sidewalk in Toronto on Monday in what was described by police as a deliberate attack.
The incident - which Prime Minister Justin Trudeau called a "tragic and senseless attack" - was one of the most violent in recent Canadian history.
Toronto Police Chief Mark Saunders said a suspect identified as Alek Minassian, a 25-year-old from the Toronto suburb, has been detained.
However, the motive of the attack is still unknown and Toronto police have no file record on this suspect, the police chief added.
The driver was heading south on busy Yonge Street at around 1:30 p.m. (1730 GMT) and the streets were crowded with people enjoying an unseasonably warm day when the van plowed into the pedestrians.
The incident occurred about 29 km from the city center, where foreign ministers from the G7 countries were meeting to discuss world issues.
Video broadcasts on several Canadian outlets showed police arresting the suspect, dressed in dark clothes, after officers surrounded him and his van several blocks from where the incident took place in the North York neighborhood of northern Toronto. He appeared to make some sort of gesture at the police with an object in his hand just before they ordered him to lie down on the ground and took him away.
Police cordoned off several city blocks and Toronto Transit Commission has sent an alert, saying that there is no subway service between Sheppard and Finch Stations as Toronto Police are conducting investigation at Sheppard Station.
"The actions definitely looked deliberate," Saunders told a news conference on Monday night close to the site of the incident.
Asked if there was any evidence of a connection with international terrorism, the chief said: "Based on what we have, there's nothing that has it to compromise the national security at this time."
"The investigation is at a stage where no further information can be confirmed at this point. The police are conducting obviously their thorough investigation to determine what happened and why it happened, the motivations involved," Canadian Minister of Public Safety Ralph Goodale said at the press conference.
"I can assure the public all our available resources have been brought in to investigate this tragic situation," Toronto Police Services Deputy Chief Peter Yuen said earlier.
At least seven people were rushed to nearby Sunnybrook Health Services Center's trauma center, the hospital said on Twitter, adding that the emergency department has been locked down as an added precaution.
Ryder System Inc spokeswoman Claudia Panfil confirmed that one of the company's rental vehicles had been involved and said the company was cooperating with authorities.
Goodale called the incident a "horrific attack" and said the G7 foreign ministers extended their condolences.
"We should all feel safe walking in our cities and communities," Trudeau said in a statement on Monday.
"We are monitoring this situation closely, and will continue working with our law enforcement partners around the country to ensure the safety and security of all Canadians," he added.