Some folks just can't sit passively when wrongs are committed.
Also, that gun looked less than real, but with that type of video, I could not tell for sure....just a lack of detail.
But, the intro said the BG had what "appeared to be a big gun" and never said he did have a gun. Perhaps the Sgt. was able to identify it as a fake gun?
I'd bet the announcers would have made the point the gun was real had that been the case and if they were aware it was.