I've been shocked about a half-dozen times in my life. It has a way of making you not want go near the same setting again.
How about some cameras and recorders since we know this is a current problem?
How about some volunteers from a distance watching for a couple of months and reporting activity?
Might not be an enviro-whacko at all;
could just be somebody sick of drivers wandering all over I-10 or 610 during rush hour blabbering on their cell phones.