The sounds like a operation from Chaos. They play the left right game all day and night. Ie Deep State. Only other plausible is a softening of the target (El Paso) with a wag the whitey play before the main attacks (AntiFa).
That is a possibility - and definitely a Deep State level of involvement. I can absolutely see them planning and carrying out something this horrific, just to run interference for AntiFa in a place where they're not welcome.
Besides all that, to them - any opportunity to sow mayhem and confusion is a good one.