There's a pic of a guy in plain clothes holding a rifle and wearing body armor. I don't think he's wearing "colors" and it seems it would be hard for him to blend in strolling around the patio with a rifle and bulletproof vest.
The speculation about him being undercover and involved is just that - speculation - and in my view it doesn't hold up.
I also think it very unlikely that the Waco PD would issue a press release stating something that would surely be dis-proven in short order once cases start going to trial.