Earlier quoted context omitted.
AT&T says that their services went down along with the gas & power in the area, as a side effect: the gas shutoff cut off their backup generators. That doesn't sound all that targeted.
While I'm only speculating, it could be quite possible that whoever may have wished to damage or destroy the AT&T building, seriously underestimated what these kind of buildings can take (essentially being disguised bunkers). This certainly wasn't a small explosion, from the looks of it. But taking out a bunker .. unless you have access to weapons specially build for that purpose, good luck. That AT&T still went down…
This really sounds like people playing with stuff they have no understanding of.