That is the rub. It seems to somewhat random.
IIRC there was a warrant out for some guy in Texas City who was seen shooting refineries from the highway. He did this at 5pm BTW. Not 4am or some ungodly hour.
I mean from what I know about Texas City you can't NOT shoot a refinery there!
In my city, Tucson, I have never had a problem. Except with the cops during protest marches, but our PD has some serious ummmm...."problems".