From the prior link provided by wishyouwerehere:
"The report, which examines comprehensive crime gun trace data provided by ATF to Mayors Against Illegal Guns, finds that the states with the weakest gun laws are the top suppliers of the guns recovered in out-of-state crimes and are also the source of a greater proportion of likely trafficked guns."
Guess where Illinois gets most of its illegal guns: Mississippi - becasue of its weak gun laws.
and from Cubby:
Chicago's homicide count eclipsed 500 last year for the first time since 2008. Chicago's homicide rate was almost double in the early 1990s, averaging around 900.
My conclusion is that most of the guns are coming from states with weak gun laws, and that Chicago has about half the murders overall from the past due to their new laws....