Not sure if a movie or a show.
Scene starts with a wealthy businessman preparing to leave for the day, exits home with chauffeur & his newspaper. Chauffeur drops man at the subway station. Man enters train, makes eye contact with small girl. Man exists train shortly after, shot shows he has left his newspaper on the train & that the girl saw it. Man meets back up with his driver. Meanwhile poison has started to be released in the train & panic follows.
A bit later someone from the train gets the attention of a safety worker at the station (who I want to say was heading home for the day) and he is pulled into helping during the chaos. I believe he was the one to find that the newspaper was the source of the gas canister.
This would be a newish (in the last 10 years) release.
Thank you for any help you can offer!