Sister now feels unsafe: Peeping Tom Situation

[Jimmy M.]

Hi, Looking for advice for my sister to get out of her lease before we contact the landlord again.  Here's the situation:  For the past few weeks, around midnight once or twice a week she thought she heard porn being played by a neighbor very loud and very clear.  She took videos, contacted the landlord, let him know how unsafe and uncomfortable she felt with this going on.  Landlord responded but did not do much or offer much guidance.  Fast forward to last night.  A neighbor next door sees a guy outside her window masturbating and playing porn on his phone.  This is clearly the situation, someone had followed her and was doing this deliberately outside her window.  A police report was filed, they took down all the information, and they think it actually is the same person who had been doing this all over Chicago.  

The unit is a 1st floor studio in a 10-20 unit building in Chicago near Wrigley Field.  

Our goal is to now contact the landlord with a clear and concise request to terminate this lease, as she no longer feels safe there..  She is going to be staying with us until we find her another apartment that is not on the 1st floor or Ground floor.  My brother is a lawyer and has offered to step in, citing clear negligence of safety after multiple requests.  What we are really looking for is guidance on how to best approach the landlord to just have the lease terminated so she can move on past this horrible experience.  Any guidance or thoughts?  

My initial idea is to try to handle it nicely, if he has another building that feels safer and not a ground floor, she would entertain looking at units there to not cause him financial harm.  I don't think in good conscious she would sublease this unit now.  

Thoughts welcome.