Katie Ledecky breaks her own world record on way to Olympic gold for U.S.

Last Updated Aug 7, 2016 11:48 PM EDT

RIO DE JANEIRO -- Katie Ledecky has given the United States its first swimming gold medal of the Rio Olympics with a world record in the women's 400-meter freestyle.

The result was totally expected. Ledecky has dominated the longer freestyle events since winning gold in the 800 free at the London Olympics as a 15-year-old.

She was doing nothing but racing against the clock Sunday night. No problem there.

Ledecky kicked off the first wall with a lead of nearly a body length and steadily pulled away from the overmatched field -- as well as the world-record line superimposed on the video screen as her powerful arms churned through the water.

Ledecky was a woman among girls on Sunday. After the first 50 meters, no competitor even came close to her side in the race, CBSSports.com reported.

When Ledecky saw the time -- 3 minutes, 56.46 seconds -- she let out an uncharacteristic scream and pumped her right fist. The 19-year-old crushed the mark of 3:58.37 that she set nearly two years ago on the Gold Coast of Australia, and had been chasing ever since.

It is Ledecky's first gold of these games and she will have three more chances later on this week in the 200-meter freestyle, 800-meter freestyle and 4x200-meter freestyle relay.

Jazz Carlin of Britain took the silver and Leah Smith of the United States grabbed the bronze.