"The best part was not just the numbers ... but the diversity of the people coming from every single community in London, coming together for this cause," said 19-year old college student Abdullah Al Jarad at the march.
The attack sparked outrage across Canada, with politicians from all sides condemning the crime, spurring growing calls to take action to curb hate crime and Islamophobia.
Veltman made a brief court appearance on Thursday and will return to court on Monday. He faces four charges of first-degree murder and one of attempted murder.
Canadian Prime Minister Justin Trudeau has called the killings a "terrorist attack" and vowed to clamp down on far-right groups and online hate.
