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The sun was just setting on Memorial Day when gunshots ripped across St. Andrew’s Playground on Atlantic Avenue in Bedford-Stuyvesant.
Three teenagers were wounded in the gunfire, the youngest being 16. It was one of six shootings during the holiday weekend that left 10 wounded and one dead in northern Brooklyn, where police have been wrestling to contain a steep rise in murders and shootings.
Over all, murders and shootings have dropped in New York City to levels not seen since the 1950s. Murders so far this year are down 11 percent over the same period last year. But the spike in shootings in North Brooklyn over the first three months of the year, peaking at 22 in March, shows that the police have struggled to contain pockets of violence, often driven by gangs.
Monday night’s shooting in Bedford-Stuyvesant appears to be part of a wave of tit-for-tat violence in the 79th Precinct between several street gangs, the police said, among them Brisp Nation, Gates Fam, Rich Fam, the Hoolies and the 900 gang.
Those rivalries have helped drive up violent crime across northern Brooklyn, and Monday’s shooting has worried officials that the borough could be in for a violent summer.
“One shooting concerns us,” said Deputy Chief Michael Kemper, the commanding officer of detectives in the precinct known as Brooklyn North, which includes neighborhoods like Bedford-Stuyvesant, Crown Heights and Brownsville. “But to have six shootings over a holiday weekend is certainly concerning.”
Why violence spikes in a place like north Brooklyn is a difficult problem to decipher and solve, and the phenomenon is not unique to New York, criminologists say.
Last summer, Chicago wrestled with a rapidly rising murder rate, mostly on its South Side, before the trend leveled off at year’s end. By fall, Philadelphia was the city with a problem. This year, both South Central Los Angeles and northern Brooklyn are fighting to contain violent streaks.
In neighborhoods like Bedford-Stuyvesant and Crown Heights, police said the spike has been driven by violence between competing street crews, whose methods have changed since the 1990s, becoming more driven by social media and less predictable.
“They have alliances, and they just don’t like one another,” said Chief Terence A. Monahan, the department’s highest-ranking uniformed officer.
Today’s street gangs overwhelmingly consist of young teenagers, with allegiances that are tied to housing developments and individual blocks, rather than to national or regional groups, the police and community groups say.
In past decades, feuds arose between gangs over control of drug-selling territory or other illicit businesses. But now beefs often blossom on social media over relatively minor matters — perceived insults or slights, investigators said. That makes the shootings more unpredictable and random and can happen in fast, concentrated bursts, the police said.
“It’s not over drugs. It’s not over anything but, ‘You’re on the opposition. I don’t like you,’” said Chief Monahan. “That’s how it starts to spiral out of control.”
Calls to action on social media often come with hashtags, as the crews air grievances and organize attacks. Detective George Harvey, who has worked in the 79th precinct, in Bedford-Stuyvesant, for 25 years, said gang members regularly post messages about disputes with other gangs, general activities and their movements.
In Bedford-Stuyvesant, the police have linked many of the percolating street feuds to a shooting from July 4 of last year, when a rival gang, believed to be the Hoolies, opened fire at an outdoor party for members of Brisp Nation, Gates Fam and Rich Fam.
“Maybe we have a problem,” Deputy Inspector Charlie Minch, the commanding officer of the 79th Precinct, recalled thinking. He was right. The ambush drove violence up that summer, and fueled the spike early this year.
From Williamsburg to Brownsville, investigators say feuds between gangs have left a trail of killings and shootings, often foreshadowed digitally on social media.
Courtney Tingle, 26, had written openly about his affiliation with the Crips on social media. He was murdered in March, just days after posting a warning that suggested a fellow Crip had made a pass at his girlfriend.
Devontee Cameron, 19, often flashed gang signs in photos he posted on Facebook. He was shot and killed in Bushwick in January.
And Davion Powell, 18, was shot and killed in broad daylight outside a Crown Heights apartment complex. He had published the name of his crew with a hashtag in posts on Facebook just hours earlier.
The most gruesome recent example of gang violence was the March murder of Tyquan Eversley, 21. In security camera videos, Mr. Eversley was seen frantically running through the streets of East New York, pursued by at least seven men. He tripped as he attempted to escape over a fence. His assailants threw a brick at him and shot him to death.
Four of those men have since been arrested and charged with murder. Mr. Eversley was targeted by a rival gang, said one law enforcement official, who did not go into further detail.
These days, allegiances to national gangs like the Bloods, the Crips or Folk Nation are often trumped by loyalties to local gangs. People often join national gangs in jail for protection, but once they return home, most rejoin the street crews they grew up with.
“These are the kids and the grandkids of the crack era,” said P.I., an outreach worker for Save our Streets Bed-Stuy, a community group that works with local teenagers to stem gun violence. “They like to think they’re gangs. Everybody’s jacking that.”
P.I. requested to be referred to only by his street name, to preserve his credibility with the youth in the area.
For the past three months, the Police Department has thrown extra resources at north Brooklyn to stem the violence. Additional patrols have been sent to housing projects in Bedford-Stuyvesant. The police have also been meeting regularly with community leaders in Brownsville.
Most significantly, in March, the police commissioner, James P. O’Neill, and the Brooklyn district attorney, Eric Gonzalez, announced a new push to crack down on gun crimes in the borough. Gun arrests have increased by 10 percent as compared to the same time last year, to 545 from 494, Mr. Gonzalez’s office said.
The police believe the approach is working, pointing to the department’s most recent crime statistics. Since peaking in March, shootings in Brooklyn have dropped. Murder numbers are returning to levels similar to the same period last year.
Inspector Minch said the department gave his precinct eight additional officers in February and planned to send 17 recent graduates from the police academy to the command. “More than I’ve ever gotten,” he said.
“It can help, having a surge in some way where you just have more visibility can displace violence, especially gun violence,” said John Roman, a professor at the University of Chicago’s Crime Lab, which tracked that city’s murder spike last year. “At the end of the day you’ve got to understand what the disputes are about, and you’ve got to understand the nature of the dispute.”