There's another, longer video of the incident which shows them pulling specific individuals off the train and arresting them.
The protests have been accompanied from the start by rock throwing and the use of laser pointers to try to blind policemen. I'm not surprised the UK police are running out of sympathy at the stage in the game.
See the incident where Officer Bald Lau Sir raises his shotgun at the crowd that garnered widespread support in mainland China. The Officer has a rather severe burn to one of his eyes from a laser. Many of those lasers are very defo not eyesafe models, look more to be 10mw plus range.