Washington - Rising homicide totals in most of America's large cities have sounded alarms within the Obama administration, with law enforcement officials trying to determine the reason.
The numbers are nowhere close to levels of the early 1990s, when the crack cocaine epidemic contributed to hundreds of homicides a year in large cities. Even so, federal officials are concerned that the current trend comes as a series of high-profile police shootings of young black men have driven a wedge between police and their communities and placed policing tactics under extraordinary scrutiny.
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Each instance of perceived officer misconduct, and each time an officer is physically attacked while on patrol, risks widening that divide, FBI Director James Comey has said.
The uptick, if it continues, threatens to draw resources away from other police department initiatives, and reverse some of the progress cities have made against violent crime over the last two decades.
Comey, testifying in Congress last week, said the "very disturbing" homicide spike has law enforcement scrambling to figure out why now, and why in so many cities that seemingly have little in common otherwise.
"It's happening all over the country, and it's happening all in the last 10 months," Comey told the House Judiciary Committee. "And so a lot of us in law enforcement are talking and trying to understand what is happening in this country. What explains the map? What explains the calendar?"
The Justice Department this month organized a brainstorming summit with mayors and police chiefs. Attorney General Loretta Lynch and President Barack Obama are scheduled to discuss criminal justice issues Tuesday at a conference of police chiefs in Chicago.
This year has brought an unusually grim and steady drumbeat of violence in the country.
A 5-year-old girl killed this month in Cleveland in a drive-by shooting. Seven people slain in Chicago over the July 4th weekend. A young journalist in Washington, D.C., fatally struck by an errant bullet in May while waiting to change buses.
Washington, D.C., which recorded 88 homicides in 2012, already has 128 this year. Chicago police counted 385 killings as of Oct. 18, up from 323 on the same date last year. Police in New Orleans say they've seen an increase from 71 in the first two quarters of 2014 to 92 in the first quarters of this year.
There's no single explanation for the problem, and it's not clear whether this year's numbers are an aberration or the start of a worrisome trend. Some blame easier access to drugs and guns and have suggested that residents, including gangs, suddenly seem more willing to resolve petty disputes with deadly violence.
In New Orleans, "community leaders emphasize to us that the majority of young men involved in these violent crimes are having a sort of crisis in their identities and their sense of being part of this community and being valued and valuing others," said Ursula Price of the office of the New Orleans Independent Police Monitor.
Some experts also think that the homicide totals had crept so low that it was unreasonable to expect that decline to continue, or theorize that police strategies may have stopped evolving amid success.
"We thought that all the things we were doing were making crime decline in meaningful, permanent ways," said John Roman, a senior fellow at the Urban Institute, a Washington think tank. "And it turned out we weren't doing as much as we thought, and the declines weren't permanent."