I'm guessing that this is yet another false flag operation. Run out of the ATF instead of the FBI this time.
The ATF is not supposed to be a first or even second or third responder... They should only be involved when local / state police want to trace how the criminals got their firearms, explosives , alcohol or tobacco.
It is amazing how quickly ATF was on the scene. Why should the ATF so quickly be involved? It’s much the same as the FBI quickly arriving on scenes practically at the time a “mass” shooting starts.