I believe that the assault only lasted for a few minutes, but, due to the head trauma I experienced, I am not 100% sure what happened. No one tried to stop him from attacking me, and I was too stunned to fight back. A female MTA worker, I later learned, called for police help immediately after she saw me get hit. I only got a chance to look at my assailant when he was running away.
Article source: https://www.huffpost.com/entry/subway-random-attack-violence_n_5fda38d7c5b610200986d404