CCTV footage captured the horrifying moment a 56-year-old man pushed a 59-year-old female rail worker onto the tracks at Yuen Long train station.
The footage, which has gone viral on social media, shows the man walking up calmly behind the woman.
Then, without warning, he forcibly shoved the woman and walked away.
A police spokeswoman said officers had arrested the man near the rail stop on suspicion of assault occasioning actual bodily harm, reports the South China Morning Post.
'The woman suffered injuries to her jaw and was sent to Pok Oi Hospital for treatment,' she said.