Firearms are not registered in Wisconsin or Illinois.
Illinois requires firearms owners to have an Firearm Owner Identification Card (FOID). I am pretty sure it does not list the firearms owned.
The requirement for an FOID is being fought in the courts.
Do you know who is fighting it? Here in New Jersey the number one gun "crime" is possessing one without permission from the almighty state. You need a permit to purchase and a carry permit if you choose to take it outside your home or business. Carry permits are almost never issued to the unconnected, and you must show a "need" to even be considered. All of that is a clear infringement in my eyes.
WI open carry law states you MUST be 18, he’s only 17
How did he get the rifle? It was purchased somewhere, whose name was it purchased under, his dad?
or did he get it “loaned” to him at the scene
Many more details to be answered, I guess we’ll find out more at his extradition hearing on Fri, he will be tried as an adult