Updated

Toronto police were investigating the possibility of gang involvement in a shooting that killed two people and wounded 23 others at an outdoor party, and said Tuesday they were concerned about the potential for violent retribution.

Bullets from more than one gun sprayed into the crowd of more than 100 people at an annual barbecue Monday night in the suburb of Scarborough. Police said two handguns were used, and one was recovered at the crime scene.

"In my 35 years of policing, this is the worst incident of gun violence in my memory," Police Chief Bill Blair said. Authorities said they had one "person of interest" in custody and were looking for other suspects.

"We are very concerned not only with the quick resolution of this crime, but with the potential for retaliatory violence, which we often see in this type of event," Blair added.

This type of brazen gunfire is rare for Canada's biggest city, which prides itself on its safety record, but Monday's melee is the fourth fatal public shooting in Toronto in less than two months. The city's latest incident raises fears that Canada could be moving closer to U.S. levels of gun violence despite the country's strict gun control laws.

Police said they suspect gangs were involved in the shooting that killed 14-year-old Shyanne Charles of Toronto and 23-year-old Joshua Yasay of Ajax.

Twenty-three others were sent to hospital with gunshot wounds, including a 22-month-old child who was grazed by a bullet and is in stable condition, police said. One person was trampled in the ensuing stampede.

Some of the wounded, aged between one and 33 years old, were treated and released. One man remained in critical condition in hospital Tuesday afternoon, police said.

Police said one injured "person of interest" is in custody.

"It's an unfortunate fact of some individuals involved in this type of violence, carrying firearms, and involved in gang activities, that they seem quite willing to engage in violence in very public settings, putting a lot of people at risk," said Blair, adding that additional officers will be stationed in the affected community, as well as where police believe retaliatory violence may take place.

Blair, who described the shootout as an "unprecedented" episode of violence, said the homicide squad, the guns and gangs unit, the intelligence services urban gang unit and divisional policing are all involved in the investigation.

Gene Jones, the head of Toronto community housing, said the victims were residents of his buildings.

"It is just kids that have guns, and shouldn't have guns, who seize an opportunity because it is powerful to have a gun," he said.

In total, there have been 29 murders this year in Toronto, including a man who was shot on a soccer field Tuesday night.

Monday night's shooting came just weeks after a gunman opened fire in a crowded food court at a busy mall in the heart of the city. One man was killed instantly at Toronto's Eaton Centre, another died days later and several bystanders were sent to the hospital. Police have said the three men involved in the incident belonged to the same gang, but believe the shooting was motivated by a personal dispute.

Following that incident, a man was shot dead on a crowded patio in a popular downtown neighborhood, Little Italy, where patrons had gathered to watch a televised soccer match.

On July 1, a man was shot in the chest after the close of a crowded fireworks display celebrating Canada Day.

Toronto Mayor Rob Ford reassured residents that the city remains safe, despite the high-profile shootings in recent weeks.

"We've had a couple of isolated incidents ... I know this is the safest city in the world, I've always said that, I truly believe it," Ford said.