Why aren't they telling us the race/nationality of the attackers in Dallas?

Something weird is going on in Dallas.

Consider this.  I've theorized that its white supremacists.  But that theory has a serious hole in it.  Why would they attack police?  They had a target rich environment of black people to shoot at.  Why go after police when you can go after your number two enemy right after Jews?

If its black people then why strike during a black lives matter protest?  You could get bigger bang for the buck and terrorize the police dept by attacking those guys on patrol.

Could it be sovereign citizens?  A terrorist group?  Even ISIS?

Something is off on this thing and the authorities are getting their story together.  The thing that has me spinning is the assault on that police officer.  That guy was trained up.  He had some good CQB, and handled his weapon well.  Additionally he appeared (from what I could make out) to be in much better shape than his victim.  

The race/nationality of the attackers will tell us much.  Why aren't they telling us?  This thing is a tragedy with a terrible smell on it.  I just can't put my finger on it.