At dinnertime in northwest Toronto, a kindergartner twirls in a princess dress on a green field while two boys play basketball on a nearby court.

But by 7:30 p.m., their mothers start calling them inside. And they don't let them back out – for any reason.

Lately, says one mother, older boys have been coming onto the field and shooting handguns aimlessly into the air.

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"I can't say if it's weekly or monthly," she said. "I just usually hear it if I'm out here smoking. I usually bring my kids in before 8, because you never know."

The field borders Jamestown Crescent, where a pregnant mother of two, Rochelle Bobb, was shot and killed Sunday night. Her baby was saved by emergency cesarean section.

The incident shook Jamestown residents and roused the rest of the city to recognize an alarming trend.

In the days after Ms. Bobb's death, Toronto recorded its 30th homicide of the year – double the number for the same period a year ago. Factor in guns and the spike is particularly glaring: 19 gun homicides in 2016 so far, a 217-per-cent increase; and 135 shootings, representing a 60-per-cent jump compared with the same period in 2015.

If the trend continues, Toronto could surpass the 2005 high of 52 gun homicides – a chapter in the city's history still remembered as the "summer of the gun." Several theories for the increased gun violence have emerged – any combination of which could help explain the bloodshed.

THE END OF CARDING

In the U.S., dozens of police chiefs and police unions have speculated that increased gunplay is a function of the "Ferguson effect" – the theory that officers are backing away from proactive policing in the face of large-scale protests against police brutality, including the shooting of an unarmed teenager in Ferguson, Mo. Perhaps the theory's most reputable voice has been James Comey, the FBI director who has said the protest movement has created "a chill wind blowing through American law enforcement."

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A similar theory has traction in Toronto, where years of controversy over the local police practice known as carding have left officers confused over how they can engage with residents, suspicious or not, according to officers and their union. "The way police are being portrayed and demonized has created a disconnect between the public and the police," said Toronto Police Association president Mike McCormack. "A lot of the major urban centres where we're seeing this, there is a slowdown in proactive policing, where police are more hesitant to engage the public."

In a recent internal TPA poll, 97 per cent of officers said they were no longer policing as proactively as they once had, according to Mr. McCormack, who did not say how many officers were surveyed.

The theory has holes, however. For one, carding in Toronto has been suspended since Jan. 1, 2015, so the 217-per-cent increase compares two periods without carding. What's more, the premise of the theory is that activists and protests have undermined the authority of police and ruined their relationship with the community. But the activists counter that police themselves are responsible for destroying their own credibility, through actions such as the Sammy Yatim streetcar shooting, the G20 kettling and racial profiling.

"They are saying that the police have no accountability, that the community has all the accountability," said Andray Domise, a community organizer. "It's a fundamentally stupid argument."

GUNS ON THE STREET

Toronto's police chief and other senior officials have argued an increase in gun seizures proves that more guns are circulating on the city's streets. So far this year, 250 firearms have been confiscated, 100 of them being handguns, according to Chief Mark Saunders.

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What is unclear is how many of these guns are considered "crime guns" – guns possessed illegally or used in a crime. Over the past four years, the number of crime guns seized has consistently been between 575 and 610. If all 250 guns seized over the first quarter of the year are deemed crime guns, then Chief Saunders's theory could certainly hold. Historically, however, the majority of guns seized by Toronto police are not crime guns; they are handed over as part of regular amnesty programs.

Neither the Toronto police, nor the OPP's provincial weapons enforcement unit, the lead agency on stopping the flow of guns, could provide specifics about where the glut of firearms is originating.

More than two-thirds of guns used in crimes in Canada can be traced back to the United States. The demand for guns among organized crime in Canada means that smuggled guns can fetch 10 times their U.S. value and can be easily shipped across the border, explained Christian Leuprecht, a Queen's University and Royal Military College political science professor who studies gun-smuggling networks.

"If you want to get weaponry – it's not that difficult to get weaponry and bring it in to the country … [Canada Border Services Agency] can't stop every car that goes across the border," he said.

Border agents, mainly at crossings in Southern Ontario, seized 261 firearms from April 1, 2015, to Jan. 25, 2016, according to data provided by the CBSA. That is up from 172 for the same period a year earlier. For the more recent period, 41 weapons were non-restricted firearms such as hunting rifles, 81 were restricted firearms such as handguns, and 139 were prohibited guns that include automatic weapons.

But the University of Toronto's Jooyoung Lee is skeptical of the Toronto polices' claim that an increased number – and greater availability – of guns is to blame for the spike in gun homicides. "I think it becomes a narrative that the police use often as a way to justify and legitimize an increase in police resources," said the assistant professor of sociology and expert in gun violence.

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HABITS OF GANG MEMBERS

Officials have blamed gangs for a number of this year's shootings. But that doesn't mean there's a new turf war – the problem is that guns are being used in new ways in old turf wars, said a police source.

After the height of gun crime in 2005, police enforcement was strong enough that gang members didn't regularly carry guns. They would stash them with friends or family.

"In order to use that gun, they would have to have a lot more planning involved, rather than being more spontaneous," said the source.

"They didn't carry it with them all the time, and they knew their rivals didn't carry it with them all the time. So instead … they would gather intelligence about where maybe their rivals are going to be, then they would go get their guns that are hidden in their girlfriend's house, then go to where those rivals might be and hopefully see them and then use the guns."

Now gang members are more likely to carry guns, "and if they happen to spontaneously see rivals, those rivals have guns as well."

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Then comes an impulsive shooting, even if bystanders may get hurt in the process.

People in Jamestown complain that gang members are younger and more impulsive than in the past – "kids doing stupid things and not thinking of the consequence and thinking they're cool," as one woman put it.

But the police source disputed that, saying there have always been very young gang members. Police suspect Quinton Gardiner, the 19-year-old charged in a double kidnapping and "gang town shootout" at a Front Street condo last month, has been involved in the Youth Buck Killas gang for years. His older brother, now imprisoned, had earlier led the gang.

"You have the younger brothers, or sometimes even sons and daughters, picking up the family business," said the source.