This one resonated with me a bit more than usual:
As Weer'd says, not a gun death so doesn't matter, right? And of course, none of the examples of this type of attack to date are known to be the result of "terrorism".
OTOH I vaguely remember news stories from the early 80's of "union thugs" tossing bricks in just this fashion into 18 wheelers driving down the interstate for not respecting their declared strike; I'm sure I heard/read stories of drivers shooting at people in retaliation, so my titular question doesn't seem all that far out of the realm of possibility to me.
Doesn't have to be the religiously motivated of course, but at some point I think it pretty likely that someone with an existential grudge is going to decide that being effective is better than being famous, and then we really will be in for it, won't we? When the daily commute routinely includes brickbats through the windshield, I'm going to go with "whatever caliber is immediately available" being the most common answer proffered in reply myself.