He was on his way to meet his girlfriend and sister at his local railway station when he heard their cries for help from a bridge overlooking the station.
A woman, who had been travelling on the same train as the girls, collapsed after it had pulled out, causing her to fall onto the tracks and knock herself unconscious.
As half a dozen shocked passengers stood on the opposite platform on a cold November evening last year, 17-year-old Carl sprinted across the station with a train due to pass through at any minute.
"I didn't even think about it really," he says modestly. "It was just instinctive. I got to the top of the bridge and saw the look of panic on the girls' faces and knew something was wrong.
"My sister shouted over to me and, after I saw the girl on the tracks, I knew I had to get to her as soon as possible."
Without realising that the unconscious woman was less than three inches from a high- voltage live rail, brave Carl jumped down onto the line. But as people panicked on the opposite platform at East Worthing in West Sussex, Carl kept his cool during the vital seconds he had to save the woman as the train approached at speed.
"I didn't know it was coming, even though there were people on the other side shouting to me," says the trainee stonemason, who lives with his dad Roger, 60, brother Daniel, 20, and sister Catrina, 15, in Sompting, West Sussex.
"She was like a dead weight, but I managed to lift her up quite easily. I suppose it was the adrenalin running through me."
Carl lifted her onto the platform and leapt clear as, seconds later, the train rushed through the station.
Simon Watson, 63, from Folkestone, who was at the station that evening, says Carl was undoubtedly a hero.
"I was shouting at the girl to get up because we knew a train was on its way, but she wasn't moving," he says.
"The next thing we knew, this young lad was racing down the platform, jumped onto the tracks and carefully lifted her off.
"There is no doubt if it wasn't for Carl, the young lady would have been killed."
Carl then made sure an ambulance was called, and paramedics took the woman to Worthing Hospital, where she was later discharged.
Proud dad, Roger, also paid tribute to his courageous son.
"To go to the lengths young Carl did, with adults standing on the other side of the platform, just goes to show how brave he was that night," he says.