On Tuesday night, at the doors to the airport’s Terminal 1, Hong Kong came within seconds of tragedy.

Pro-democracy protesters had held the airport for hours, as they had the night before, causing the mass cancellation of evening flights.

But unlike the previous night, they had also taken a captive.

Members of the young crowd were wired and on the lookout for suspected infiltrators after policemen disguised as protesters made a number of surprise arrests the weekend before. Some time after 6 p.m., they found and hogtied a man they believed was a Chinese policeman. To the sound of loud chanting, they beat the man and paraded him around the airport until he was unconscious, then blocked paramedics who took hours to wind him out of the jammed hall.

Police didn’t arrive for several hours. Eventually, a lightly armed contingent in the force’s familiar blue shirts helped get the man into an ambulance. As the police attempted to leave, protesters set on them as well, blockading the way forward and pounding a police van as it sat in the roadway.