Im not sure I completely agree with you. As some have pointed out, it could be a brilliant disguise. But then the question would have to be who and why.
That said, I mostly agree with you. My gut feeling is, that this was some random nut job who broke into the church, as part of some weird SWAT fantasy. Its just too weird, and doesnt make any sense.
That's my gut, too. In the most recent video the person looks like they are doing a routine security check. Wouldn't think someone who was trying to rob the place or waiting to commit murder would bother. Bringing in the ATF and a 3rd federal agency as well as the dog has me thinking it might be something more.