"When I was taking a picture next to the timer, I actually cried."
Aged 16, Athing Mu is already an American record holder.
At last month's American Indoor Championships, she clocked one minute 23.57 seconds to win the women's 600m.
The event might not be in the Olympics or World Championships and so is staged rarely but Mu's time is an American indoor record and the second-fastest indoor time in history. It has been said her time equates to doing an 800m in one minute 57 seconds - potentially a championship medal-winning time.
Her assistant coach Bernice Mitchell was not surprised, saying: "I've been telling her she's been amazing since she was six and people were telling me I was crazy."
BBC World Service's Ed Harry spoke to the New Jersey teenager dreaming of Olympic glory.
'I'd tag along with my brother... I've been there ever since'
Mu is the second-youngest of seven siblings in a family of Sudanese heritage.
As a child she would watch her brothers at Trenton Track Club, and soon started running herself.
"All of my siblings have run track," she says. "The eldest, he's 26, actually started off the running.
"When he used to go to Trenton Track Club, he'd tag me along and I'd just be running round the track. I've been with them ever since."
Mu is a pupil at Trenton Central High School, but does not run for their track team.
She says: "Since freshman year, the coaches have been trying to recruit me but I've just preferred to run with my club since I've been doing so well with it."
'Every single day it just sinks in a little bit more'
In an incredible weekend in New York, Mu lowered her 600m best by almost four seconds. Russia's Olga Kotlyarova - who clocked 1:23.44 in 2004 - is the only woman to have run the distance quicker.
"I was very, very, very, very surprised," says Mu, who is nearly 6ft tall. "I honestly didn't expect that.
"After I ran I didn't really get to talk to many people because I had to go to straight to drug-testing.
"I didn't really get that feeling of 'Oh my gosh, I'm so known or I'm so famous.' Going home, it definitely felt pretty normal.
"I think every day it just sinks in a little bit more; I'm just actually coming to a realisation of what I did."
'Being in high school levels out my amateurism'
Honours student Mu, who says her favourite subject is biology, says school life hasn't changed since her record-breaking victory.
She also has no immediate plans to turn professional.
"I think high school definitely levels out my amateurism," she says. "If I were to be 16 years old and a pro runner, it would be really hectic.
"Being able to be in high school and finish off as an amateur within the next two years lets me still have fun with what I'm doing rather than be so hard on myself and have so much pressure."
'I'm here because I've made it and I'm supposed to be here'
Last year, Mu won silver in her first international event - clocking 2:05.23 in the 800m at the Youth Olympics in Argentina.
"It was very nerve-wracking going into the first race because I just thought about everything too much," she says.
"Going into the final, I regained myself and realised I'm doing this for fun and I'm here because I've made it and I'm supposed to be here.
"I chilled out a lot more and ran a much better race. It was a good learning experience."
Chasing her dreams
Mu, who favours the 800m but also has ambitions as a 400m runner, says she is inspired by Madeline Manning, who in 1968 became the first American woman to win the Olympic 800m.
"I would love to win an Olympic gold medal. I would definitely want it to be the 800m, and also it would be pretty awesome if I am able to have a world record as well," she says.
"I just hope that one day I can follow after [Madeline] and do the same thing."