Plenty of things can happen under the cover of darkness.The rioters have nothing to lose. Nothing. That is why they do illegal things because they have nothing to lose.
The people with guns have a lot to lose. They can (and would would) lose everything they have built up over their lives. If they were arrested it would cost them all their life savings to fight the law. They would lose it all and their children would receive nothing . So by acting they would destroy their own lives (which could likely be okay with with them) but would also hurt their children. So they do nothing unless it is a very last resort.
It is always the same. The bad guys have nothing to lose and the good guys have everything to lose.