Five people were injured after gunfire erupted at a packed club in the York University Heights area early Monday in a shooting that the city's police chief called "brazen."

"I find it disturbing when you've got over 100 people and someone would be brazen enough to pull out a gun and start shooting," Toronto Police Chief Mark Saunders told reporters at a news conference called to address the gun violence Monday.

The shooting occurred at around 2:15 a.m. inside the District 45 nightclub on Finch Avenue West, near Keele Street.

Toronto police said they received multiple calls about gunfire inside the club.

"When officers arrived on scene we located three gunshot victims," Insp. Stacey Davis said. "Two other victims walked into one of the local hospitals, also with gunshot wounds."

There were at least two male and two female victims, according to police on scene.

One of the victims sustained life-threatening injuries, but has since stabilized and is expected to survive police said.

Police said that two other victims had also gone to hospital with gunshot wounds, but later said they could not confirm whether they were shot at the nightclub.

Davis said officers located the shooting scene at the back of the nightclub and found shell casings.

She said the shooting occurred when the venue was still packed.

"It had not started to shut down yet, so the club was completely full," Davis said.

She said investigators will be reviewing video surveillance from inside the club.

Saunders later said that shell casings were located both inside and outside of the club.

'You could see the gun smoke': witness

A woman who was inside the club didn't want to be identified, but told CP24 that the DJ called for security before a "chaotic" scene unfolded inside the venue.

"We were partying and the music was going and then the DJ goes 'security to the back, security to the back' and then he continues playing music," she said. "Then he stops again and goes 'security to the back, security to the back' and now the music cuts off."

She said soon after that people at the back of the club dropped low and frantically tried to exit the building. At that point she and her friends "just ran."  

"After they shot you could see the gun smoke in the club," she said. "There were a lot of people and the fear in everybody's eyes... Everybody just wanted to get out and we just thought we wouldn't get out. It was one door we were all trying to get out of and if you got up you could get shot. It was just chaotic."

Saunders 'disturbed' by gun violence

The nightclub shooting marks one of eleven gun incidents that have occurred in the city over the long weekend, Saunders said. Across those incidents, 13 people were injured by gunfire and four of the shootings have resulted in multiple victims.

Reflecting on the violence, Saunders said "this is not the city of Toronto" and added that the wave of gun violence is not typical for a weekend in the city.  

"When I've got 13 people right now in the city that have been shot, that have a bullet in them, I've got concerns about that and I can tell you we will be putting additional resources in specific places that we think will help deter and reduce the gun violence that's occurring in the city right now," he said.

Saunders urged witnesses who may have fled the scene to come forward

"We think this one is very solvable. There were a lot of people that were there and some people no doubt who were afraid. We're asking you to call police," he said.

He added that police have "a lot of resources on this one and we will be in good shape to solve this one if we have witnesses come up to help."

A few hours after Saunders spoke to the media, another shooting happened in the Lawrence Heights area that injured two people.

On Monday night, a person was located with gunshot wounds in the area of Scarlett Road and Braeburn Avenue.

It brings the total number of gun incidents to 13 and the number of victims to 16.

In a statement release Monday, Mayor John Tory called the recent gun violence "absolutely unacceptable."

"I know Toronto Police are working non-stop to find those responsible for these shootings and to bring them to justice. I urge anyone with information that could help investigators solve these shootings to call police or Crime Stoppers," Tory said in the statement.

Tory renewed his call for a handgun ban as a way to help curb gun violence.

No arrests have been made and there are no suspect descriptions available so far.