Seems plausible that he was undercover but we don't know. When was this photo taken? Is it possible that he wasn't there when the action went down but arrived as backup?
Again, why are both pant legs messed up?
Burning an undercover as backup would be a pretty dumb move. But, I can accept it as a possibility. As to source / timeline - I do not know. I can search and see if I can find the original.
Law enforcement officers talk to a man near the parking lot of a Twin Peaks Restaurant Sunday, May 17, 2015, in Waco, Texas, after a shooting involving rival biker gangs. (Rod Aydelotte/Waco Tribune Herald via AP)
http://www.myfoxmemphis.com/story/29092318/photos-biker-gang-shootout-in-texas