Maybe it is the splintering of established drug gangs that has young men grabbing the tools of their trade -- handguns -- to jockey for position? Or it is that rival gangs, once miles apart in different public housing complexes, suddenly finding themselves sharing the same street corner?
Whatever the reasons, Chicago has seen a spike in its homicide rate -- with eight killed and at least 35 wounded in a spasm of gunfire last weekend alone -- that has authorities scrambling to put more police on the street and some frightened residents retreating deep into their homes.
To be sure, the violence is nowhere near its historical peak of the early 1990s when Chicago recorded roughly 900 homicides per year. But from Jan. 1 through late May there were 203 homicides, an increase of more than 50 percent over the 134 during the same period in 2011.
And in some neighborhoods, just miles but a world away from the gleaming lake and lush parks of which the city is so proud, gunfire has produced the kind of death toll that would alarm entire cities.
In Englewood, a roughly 20-by-20 block South Side neighborhood, homicides jumped from 40 in 2010 to 60 last year -- an increase that almost equals the tally of 21 homicides in the city of Seattle for the whole of 2011. The total number of homicides in cities such as Cleveland, Milwaukee, Washington, D.C., and Kansas City, Mo., each barely double the toll in Englewood.
Mayor Rahm Emanuel has made combatting gangs a priority and has stood with Police Superintendent Garry McCarthy to unveil a plan of attack. Among the new police tactics is the deployment of dozens of specialized undercover officers to units on Chicago's West and South sides and saturating those neighborhood streets with uniformed cops.
In addition, Gov. Pat Quinn on Monday signed into law the Illinois Street Gang RICO Act, which aims to dismantle gangs by boosting penalties for crimes performed as part of a criminal enterprise.
Though police are loath to attribute this winter's unusually warm weather as a possible factor, because it smacks of excuse-making, there were far more people on the streets in January, February and March -- including gang members -- than during those months in 2011.
Just as important have been dramatic changes within the gangs themselves.
"In the past the gangs were very organized from the top down," said Sgt. Matthew Little of the Chicago Police Department's gang enforcement unit. As more gang leaders are arrested, convicted and sent to prison, the gangs they left behind have become "very splintered," he said.
Young men on the city's streets agree.
"There is no one to control this, so it has become haywire," said Devon Tims, who identified himself as one of the Chicago Vice Lords, making him one of the city's estimated 70,000 gang members.
In interviews, McCarthy said the "fracturing" of larger gangs into smaller ones has doubled the number of factions and conflicts. "These kids have guns and they end up using them," he said.
McCarthy said the gangs are far more territorial and rigid than those that operated when he was a ranking commander in the New York City Police Department and the chief in Newark, N.J. And that means trouble when a gang member simply crosses the street into rival territory.
"If we see a car with three of (one gang's) guys three blocks over there (on another gang's turf), they are probably going to shoot someone," said Leo Schmitz, a gang enforcement commander who was redeployed in January to command Englewood's police district.
The demolition of the city's infamous public housing complexes in recent years also played a role. While the high rises long were considered a massive failure that warehoused the city's poorest families and became magnets for gangs, tearing them down caused a new set of problems by scattering gang members to other parts of the city.
Some of them eventually settled in the thousands of houses that were abandoned during the nation's recent financial crisis. There the battle for supremacy started anew.
Residents complain that the fear of stray bullets forces them to stay away from windows in their own homes.
"People don't give a damn, they just shoot you across the street, they come into your house and shoot you," said 80-year-old Homer Wright, whose illegal handgun was confiscated by police in April after he shot a teenager he said had broken into his tavern.
Similar campaigns to combat gang violence have been introduced in
the most violent neighborhoods over the years and Englewood residents were both hopeful and skeptical about the latest one.
Jean Carter-Hill, an activist from Englewood, said she thinks the increase in officers patrolling the streets is helping clean up the area but that the city needs to do more, such as helping youths with conflict resolution.
"Every time there is a conflict, these young people get a gun," she said. "And everyone seems to know where a gun is."