Rising homicide totals in many large American cities have raised alarms within the Obama administration.
Federal officials have been drawing attention to the problem, with the Justice Department convening a summit for police chiefs.
On Tuesday, Attorney General Loretta Lynch and President Barack Obama are expected to discuss criminal justice issues at a police chiefs' conference in Chicago.
There's no single explanation for the spike, but FBI Director James Comey last week called the trend "very disturbing."
He said officials are trying to figure out why it's happening this year and in cities that seemingly have little else in common.
He also speculated that some officers may be afraid of having an encounter on the street turn into a viral video and are anxious about getting out of their cars.