This has all the hallmarks of a lone wolf self-radicalized (but inspired by an outside group) attack from someone who wants to send a political message. Which would make it a terrorist attack.
Of course, the shooting at the Charleston Church met all the same criteria yet for some reason the Feds didn't consider that a terrorist attack.
I doubt all the people who said Charleston was the collective fault of "American White supremacist society" will be saying this attack was the result of religiously fanatical Muslim society.