Elite Hong Kong police chasing radical protesters entered a train on Saturday night, clubbing people wearing masks with batons, pepper spraying them, and making arrests in unprecedented scenes of violence and chaos.After police fired tear gas and deployed water cannons on Hong Kong Island to disperse rampaging protesters – who took over roads, threw petrol bombs and set barricades on fire – the battlefield moved to Kowloon.Video footage showed members of the Special Tactical Squad, known as …