I don't know if the thug was triad, paid, or a non uniform cop. We can't have this happen of course in a civilised society. What the city should have done is to to state clearly the protestors have a limited time to express their views, perhaps a week and then will need to scatter. Beyond this set time limit then the cops will set off on horseback and batons, bulldozers, whatever like NYC or where ever. HK did not do this because of potential global criticism and the inevitable finger pointing and aha's due to the land up north. This was a mistake by the weak HK government not to lay down rules.We are not talking about the 3rd world where US backed secret police cut off children's arms.
This protest which started out in one confined area did not draw the desired political effect so the organisers decided to spread out into multiple areas hoping to thin out police presence. In Mongkok the protestors were entering local shops occupying private space to disrupt normal business. When critized the response was hey you so selfish this is for democracy. The triad collect protection money from these shops and they do what they do.
The plan was to create as much havoc as possible in many areas so police can no longer respond to those or any real emergency thus prompting a PLA presence much like the National Guard in the US are called in for the New Orlean riots. The PLA presence would have been a goldmine in propaganda value to the Dems and other groups. Of course the powers that be did not take the bait. Ultimately the organisers wanted a second 6/4 to take the issue as far as possible. Further violence would have targeted the PLA to in order to prompt this response,