If they find out who did it, and they try to prosecute the person criminally, I wonder what the 1st Amendment Freedom of Speech implications will be. This isn't exactly yelling fire in a crowded theater.
Perhaps the posters who are attorneys can best answer this. It seems that that since this statement was not made in a public forum but over a system in a store that would be differences in the application of the law and its intent.
I think that the local store officials know who made the statement but are not saying anything in order to save face.