I didn't find this suggestion with the search engine. Sorry about the rep if it has been suggested
Since high profile shootings and robberies tend to take place in "gun free" environments, there may be some case law to be made when these things happen in businesses that post signs that create a criminal offense ref: licensed concealed carry. It would be a good idea to get photographs of such signs that identify the exact business/location. They should be date-marked to indicate that they were in place at the time of the perpetration and witnessed.
Since high profile shootings and robberies tend to take place in "gun free" environments, there may be some case law to be made when these things happen in businesses that post signs that create a criminal offense ref: licensed concealed carry. It would be a good idea to get photographs of such signs that identify the exact business/location. They should be date-marked to indicate that they were in place at the time of the perpetration and witnessed.