A 20-year-old suspect wearing a vest "like body armor" fled the scene after the attack on Sunday evening, and was arrested at a mall seven kilometres (four miles) from the intersection in London, Ontario where it happened, said Detective Superintendent Paul Waight.
"There is evidence that this was a planned, premeditated act, motivated by hate. It is believed that these victims were targeted because they were Muslim," he told a news conference, France 24 reported.
The names of the victims were not released, but they include a 74-year-old woman, a 46-year-old man, a 44-year-old woman and a 15-year-old girl -- together representing three generations of the same family, according to London mayor Ed Holder.
A nine-year-old boy was also hospitalized following the attack and is recovering.
"Let me be clear, this was an act of mass murder perpetrated against Muslims, against Londoners, rooted in unspeakable hatred," said Holder.
Identified as Nathaniel Veltman, the suspect has been charged with four counts of first degree murder and one count of attempted murder.
Waight said local authorities are also liaising with federal police and the attorney general about adding "possible terrorism charges."
At about 8:40 pm on Sunday (0040 GMT Monday), according to police, the five family members were walking together along a sidewalk when a black pick-up truck "mounted the curb and struck" them as they waited to cross the intersection.
Waight offered few details of the investigation, but noted that the suspect's social media postings were reviewed by police.
The attack, which brought back painful memories of a Quebec City mosque mass shooting in January 2017 and a driving rampage in Toronto that killed 10 people in April 2018, drew swift reactions.
The National Council of Canadian Muslims said in a statement it was "beyond horrified and demands justice" for the family who were just "out for a walk" on a warm spring evening.
MA/PR