These things seem to spawn copycats, like school shootings. Once the idea is planted...
But so far this currents spate is nothing compared to the freeway shooting spree in the '80s. In 1987 there were
more than 50 of them in Southern California. If you've seen the movie you may recall a scene in
L.A. Story that spoofed on that spree.
The one mentioned up here in the Bay Area was actually the second within a week but it turns out the first was a targeted attack.