Videos of police extremism in the Hong Kong subway
In case you've not been watching.  No need for further comment on this. 
If you can get this from the New York Times, it is a chilling video of a student
protester talking about his actions.  He seems to treat the protests as an
extracurricular activity.  Not to doubt his sincerity, but he really could be killed
in this confrontation, and I doubt that has sunk in.  A bit like Tian'anmen or
Kent State.
Update:  The anthem, written hastily but embraced by those in the streets, in Cantonese, pointedly not in Mandarin -
Glory to Hong Kong
A version with English subtitles