Interim police Superintendent John Escalante has blamed gang disputes for the spike in violence so far this year. He has noted that the conflicts often escalate through social media platforms like Twitter and Facebook, where gang members threaten and taunt each other.



Some law enforcement officials have mentioned the "Ferguson effect," a supposed tendency by some officers to second-guess themselves for fear of getting caught doing something perceived as criminal. The term was coined after the 2014 killing of an unarmed African-American teen by a white police officer in Ferguson, Mo., sparked national protests.



But criminologists have said there's no empirical proof that this is contributing to a rise in Chicago's violence.



Escalante has denied that officers are being less proactive on the streets. The department reports that there has been a 29 percent increase in murder arrests so far this year, a 12 percent increase in robbery arrests and a 9 percent increase in criminal sexual assault arrests.



The interim superintendent has temporarily moved 380 officers from foot patrols and 70 of their supervisors to vehicle patrols to enhance visibility in crime-plagued neighborhoods, police officials have said.



The shift from foot patrols comes at a time when the department is being investigated by the U.S. Justice Department for the way its officers handle police-involved shootings and how they interact with citizens, particularly in African-American and Hispanic neighborhoods.



The patrols were initially put in place in 2013 by former Superintendent Garry McCarthy to give graduates of the police academy more positive interactions with those people in crime-plagued communities.



In January, the department also started going on missions with Cook County sheriff's officers on the West Side to combat gang violence and confiscate illegal guns.



In addition, Escalante has ordered the department's 22 district commanders to increase home visits to known gang members in the neighborhoods they oversee.



At an event on Thursday, Mayor Rahm Emanuel was asked by a reporter whether the police are being less aggressive on the streets because of the release of dashboard camera video showing Chicago police Officer Jason Van Dyke shooting 17-year-old Laquan McDonald 16 times, killing him.



"Those responsible for the shootings are the gangbangers. Those responsible for the shootings are the illegal guns that are coming into the streets of the city of Chicago in the hands of gangbangers," Emanuel said. "And there's not comprehensive gun legislation throughout the state that would actually stop that.



"So the people responsible are not the police officers. I put the onus and responsibilities on the gangbangers who are pulling the triggers. They don't get a pass on accountability."