The photo of the weapon supposedly used in the shooting appeared to me to be a Saiga A 47 semi auto. Most said AK 74 but I own a 74 and it did not appear to me to be one.
Here’s some more sources, don’t know if they’re piggybacking or if they did their own research:
http://lawofficer.com/2016/07/exclusive-photo-of-the-saiga-ak-74-rifle-used-at-dallas-shooting/
https://www.thetruthaboutguns.com/2016/07/jon-wayne-taylor/dan-edit-post-please/