Ontario's Special Investigations Unit (SIU), which probes police-involved shootings, said the suspected gunman, 29, is also dead.
Two have died and at least 13 people were hospitalized following a mass shooting in a busy downtown area of Toronto Sunday night.
The suspect, armed with a handgun, opened fire at 10pm on Sunday on a stretch of Danforth Avenue filled with restaurants and family-friendly attractions in the city's Greektown neighbourhood.
Hussain's family says he struggled with psychosis and depression throughout his life, and medications and therapy didn't work to treat him.More news: Fortnite 1st Birthday Celebration Cosmetics and Challenges Announced
"We are at a awful loss for words, but we must speak out to express our deepest condolences to the families who are now suffering on account of our son's horrific actions".
"My thoughts are with everyone affected by the awful tragedy on the Danforth last night in Toronto, and may the injured make a full recovery", Trudeau said on Twitter. Toronto police have not yet revealed the identity of the suspected shooter or commented on the motive other than to say they are looking into all possibilities and not ruling anything out.
An army of police, paramedics and other emergency personnel soon descended on the scene, while area residents, some in pyjamas, emerged from their homes to see what was happening. Earlier reports said nine people had been shot.
Investigators said six women and seven men ranging in age from 17 to 59 suffered injuries ranging from minor to serious in the shooting. Local politician Nathaniel Erskine-Smith confirmed the 18-year-old victim was Reese Fallon, a recent high school graduate who planned to study nursing. The condition of the other victims was not known yet.
"We heard a woman yell help".More news: US Urges UN to Keep Tough Economic Sanctions on North Korea
'Why does anyone in this city need a gun?'
Toronto Mayor John Tory called the shooting an "unspeakable" act and said the time had come to confront the rising prevalence of guns in the city, which has experienced a spike in shootings in recent weeks. Authorities have not disclosed a motive, but said the arrested driver, Alek Minassian, posted a message on social media referencing a misogynistic online community before the attack.
"If we can prevent even one of these incidents, then it is a discussion worth having", he said, "This city has a gun problem, in that guns are far too readily available to far too many people".
Ontario Premier Doug Ford said the confidence that Toronto is a safe city has been shaken.
Canada's newly appointed minister of border security and organized crime, Bill Blair, who has been given the job of tackling gun violence, was to meet with Tory on Monday afternoon.More news: Israel Passes Contested Law That Defines It as a 'Jewish State'