It sci-fi/horror B movie frome the 70/80s…

All I can remember about this movie is that it’s about some kind of mind control experiment on a whole city.  There is a grey-ish van with a red light and some kind of antenna in it, that during the night emits something that makes people crazy.

Night after night people start get more and more insane.

In the end the whole city is totally mad and they end up killing each other very gruesomely in some kind of industrial shed or something.

I’ve been searching for months, it’s driving me insane! Does the description ring a bell to anybody?