Even though I think religion is the cause of a host of ills; I don't think we have enough evidence to say that was the driving force in this case. It could be lone nut job or religious wacko, or a combination of both. We just don't know yet.
I don't see this as any more of a casus belli for the anti-gun movement than any other incident. By that I mean I don't think they'll get any more attention or traction than they have with other similar mass shootings.
I do see a possible 1st amendment backlash against Muslims. Probably a 4th amendment backlash as well. Though that amendment is close to moribund as it is.