I am kind of amazed that the focus has quickly gotten away from the actual criminals here (the gangbanger punks) to the landlord. This is not to say that the landlord is not an issue. But somehow a gang banging kid had access to a gun! And it sounds like this is an ongoing problem with this family. For all the crying about gun control, here is a chance to use the laws on the books. Was this a gun this kid stole? Or did an adult have an FOID card and legally own it?
Politicians talk about "responsible" gun laws. We have them. Enforcement them!
They really go hand in hand. Often, landlords do not know or understand how to seek out good tenants. Or they're absentee and do not care who they rent to. Measures to improve rental housing as a whole should focus in some measure on landlord education and, where possible, landlord incentives to improve properties. The end result is better tenants.
The Village of Oak Park generally and the Oak Park Regional Housing Center in particular were very successful with this approach. Simply coming down on bad tenants is just reactionary, and doesn't really get at the root of the problem -- why they're there in the first place.