Federal agents have tracked the gun that killed a high ranking Chicago Police Officer to a house in Milwaukee.
Commander Paul Bauer was murdered while chasing a man earlier this month.
The Chicago Tribune reported Wednesday that gun was originally bought legally outside Madison in 2011.
In 2015 it was traded at a gun club. Last year it was sold over the internet to a man in Milwaukee.
The Tribune reports that man is a convicted felon. Federal agents raided his home on Feb. 16 finding 30 guns and body armor.