I don’t know about this particular case. So my post here is not meant to apply to it.
As a general comment, I know some concealed-carry guys who will “accidentally” reveal their concealed weapons. I guess it’s some sort of ego thing.
If your gun is supposed to be concealed, conceal it. It’s your responsibility, period.
And opens them up to charges of brandishing or disturbing the peace, at the discretion of the officer. Open carry is not legal in Denver. If Bob434 is correct that his tshirt was tucked in, even if he had an overshirt that was blown open, that's a problem. At the discretion of the officer. No disrespect to officers, but I'd rarely act in a way which requires their discretion, particularly in a liberal urban area.