On Saturday evening, doctor and Leytonstone resident Matt Smith was taking his usual tube journey home after an 11-hour shift when he got off the train to find a "commotion" at the station.
"There were people shouting 'someone's got a knife' and 'don't go up there'," Smith told BuzzFeed News.
A man had just attacked commuters with a knife at Leytonstone tube station, and a 56-year-old man was suffering "serious wounds".
Smith told us about the moment he discovered the injured man as he travelled home from work: "I got to the bottom of the stairs where the ticket barriers are and there was a man on the floor clutching his neck with a pool of blood around him."
Another man was trying to stem the bleeding with his jumper, and Smith said he looked very relieved when he told him he was a doctor and offered to help.
"I obviously didn't have equipment or a first aid kit on me, and I had my stethoscope, but there was not much good I could do with that, so I just sat with him, keeping pressure on the wound so he didn't lose blood, and called an ambulance."
Thinking the attacker had gone, Smith waited at the bottom of the stairs, "but then the attacker came back down the stairs towards where we were. We were one side of gates and he was getting closer to other side, with just the barriers separating us."
Smith remembers most people running back towards the train platform as the attacker shouted and swung his knife, while some "brave" others confronted him.
"Your gut reaction is to run but I didn't want to leave the man," Smith said, so, having established that the injured man was still able to walk, he helped carry him to the relative safety of the platform.
He checked the man's vitals while the commuter who had initially come to the man's rescue continued to apply pressure to his neck.
"Then we just kept an eye on him while we waited for the paramedics to arrive, making sure he didn't have a cardiac arrest.
"It was probably only about 10 minutes that it took them to get there, but it felt like 10 hours."
The man was taken to an east London hospital where he remains in a stable condition, police said. His injuries are not thought to be life-threatening.
The attacker was arrested at the scene after police restrained him with Tasers.
Scotland Yard is now investigating the incident as an act of terrorism, and on Monday, 29-year-old Muhaydin Mire appeared in court, charged with attempted murder.
Fellow doctors on Facebook praised Smith's efforts in attending to the injured man, and one post calling him a hero was liked more than 2,000 times.
After the recent attacks in Paris, NHS medical director Sir Bruce Keogh questioned last month whether doctors would respond to an attack if strikes over changes to their contract were to go ahead.
"Will junior doctors, who would otherwise have been rostered for duty, make themselves available to respond in a timely way, within one hour of a major incident being declared?", Keogh wrote in a letter to the British Medical Association last month.
Doctors, including Smith, were outraged by Keogh's comments at the time. "Nobody goes into medicine with a desire not to do good and help people," Smith told us. "For [health secretary] Jeremy Hunt and Bruce Keogh to say we lack vocation is insulting."
Smith said any doctor would have acted in the way that he did on Saturday night.
"Hopefully this will show them that we do have a sense of duty," he said.