First off, there's only been one school shooting, which doesn't really translate into "targeting schools."
Second, you've made too big a deal about "moving targets." But the shootings have predominantly targeted people who were not moving much -- such as people at gas stations, or sitting on benches, or the woman who was standing at the back of her minivan. The one school shooting is odd not just because it was the only school shooting, but also for the reason that the kid was moving.
Third, you've made too much of the timing w/respect to the tanker attack. First off, the shootings started first. Second, they involved a non-American target. Third, they happened 10,000 miles away -- it's better viewed as a coincidence.
Fourth, the ballistics guys have traced 8 of the shootings to the same gun, meaning the same person/people are probably involved in all cases. One would expect a few more terrorists to be out there shooting, and different weapons to be involved.
Finally, there are instances of serial killer "teams", including a young guy and his girlfriend who in the '50s killed several people from long distance, using a rifle.