I live in the state of Illinois, and there is a man who I believe to be a threat to myself and others around him. We both live in the same apartment complex but different apartments. He has been diagnosed with mental illness, and has been self medicating with illegal substances and not taking the medicine prescribed to him. He has outbursts of paranoid rage and has even gone so far making his roommate strip down so he could check for recording devises. He has been talking about getting a gun, and has been talking to himself in public as if he's talking to voices in his head.
What can be done in order to ensure the safety of those around him? Who should be contacted in order to report him?