Toronto police Detective Rob North said at least two guns were used in the 8 p.m. Saturday shooting that left Michael Nguyen, 23, dead just outside the southwest end of the Yorkdale Shopping Center. North said Nguyen was "known to police."
The surviving victim, a 24-year-old man whose name wasn't released, was hospitalized in stable condition.
"He is expected to survive," said North, who told reporters police were looking for "five or six suspects."
QMI Agency reported "several" guns were used in the attack.
After initially saying the confrontation began inside the mall before moving outside, North later said it was unclear where the incident began.
North said there was no indication the shooting was gang-related, but it was not a random act of violence, the Canadian Broadcasting Corp. reported.
"This was an isolated incident between two groups," North said. "We're not talking about people who come here and shot random people coming out for an evening with their family."
Shortly after the shooting, all entrances to the mall were closed and hundreds of people were forced to remain inside. The mall's parking lot was cordoned off, blocking in hundreds of vehicles.
Like all Torontonians, we were shocked by the incident that occurred," Yorkdale officials posted on the mall's Twitter feed.
"We take security at Yorkdale very seriously."
The shooting occurred less than one year after one man died and seven others were wounded at a shooting at the Toronto Eaton Center mall, the CBC reported.