Toronto police Det. Rob North says 23-year-old Michael Nguyen died after getting shot in the Yorkdale mall parking lot near a store entrance around 8 p.m.
North says Nguyen was known to police but added there is no indication the shooting was gang related.
He says a 24-year-old man was shot near a restaurant entrance as the dispute moved across the lot, and is in critical but stable condition in Toronto hospital and is expected to survive.
He says the shooting began with an "altercation" between two groups, though investigators are not sure if the dispute began inside or outside the mall, or if the shots came from opposing sides or instead members of the same group.
There were no gun shots fired in the mall and police have no information that any bystanders were injured, North said at a news conference hours after the shooting.
Police are looking for five or six suspects. North told reporters later Sunday that no weapons have been recovered at the scene.
A vehicle of interest was towed away by police for further examination, he said.
"The priority for us is to gather as much evidence as possible," he told reporters Sunday, noting a "large quantity" of footage from mall surveillance cameras was being looked through.
Police have been checking vehicles in the parking lot, and held a number of cars at the scene overnight.
Those whose vehicles were parked in the mall's north and underground lots were allowed to remove them early Sunday morning.
Dozens of officers from neighbouring divisions have been reassigned to help examine the scene and collect evidence.
The mall's management expressed shock over the incident in a statement released Sunday.
"We take security at Yorkdale very seriously in order to keep our customers safe," the statement read.
"We have regular patrols in the parking lot, well trained personnel inside and outside of the shopping centre, and security cameras monitoring most areas of the property."
Note to readers: This is a corrected story. An earlier version said the deceased was 24 but police have clarified his age as 23.
Also on HuffPost