I think that is what LE is afraid of. I think they have known for some time that this is foreign terrorism but are more afraid of the public backlash if that is disclosed.
I also find it very strange that a local sheriff is the point man for an investigation that clearly should come under the jurisdiction of the Federal government. Could it be that they are desperately trying to present the image that the Feds are not as concerned about this as they really are?
I don't think that is the reason. It's plain old CYA. They know this is a lose/lose proposition and it will be Moose's career that ends. He's just the scapegoat.