Let's not get carried away.
This dubious Red Statearticle suggests that the drop in homicides in Chicago during the first three months of 2014 is attributed to the recent implementation of the issuance of concealed carry licenses in the state.
This might be an interesting hypothesis, except for the fact that the “first wave of concealed-carry permits” was not mailed until the last week in February. And for the fact that the number of shootings had already fallen “24% from 2,448 to 1,864 between 2012 and 2013”. And for the fact that nearly $100 million was paid in overtime for officers and policing strategies that were implemented specifically to target gun violence.
Crimcast suggests a review of the problem of extraneous and confounding variables would be appropriate here.