American and defending Olympic champion Katie Ledecky was shocked in the women's 400-meter freestyle in the Tokyo Games on Monday. She finished second to Australia's Ariarne Titmus.

Titmus, who trailed Ledecky at the halfway mark of the race, turned on the speed to finish with a time of 3 minutes, 56.69 seconds, good for second-fastest all-time. Ledecky remains the world-record holder in the event.

Ledecky finished with the fourth-fastest time ever, 3 minutes, 57.36 seconds.

"I fought tooth and nail,'' Ledecky said. "She definitely swam a really smart race. She was really controlled up front. I felt pretty smooth and strong going out and flipped at the 300 and it was like, 'Oh, she's right there.'"

However, Team USA took gold in the men's 4x100-meter freestyle relay. Caeleb Dressel swam the first leg in 47.26 seconds to give the Americans a lead they would not relinquish. Zach Apple's anchor leg of 46.69 clinched it after Blake Pieroni and Bowe Becker's middle legs.

The U.S. men finished with the third-fastest time of 3 minutes, 8.97 seconds. Italy took silver and Australia bronze.

Dressel is attempting to win six gold medals; he has three individual events and two more relays to go.

In all, Americans brought home three gold medals on Monday, bringing their gold-medal count to seven -- one behind host Japan. Overall, the U.S. is second to China in the medal count. China has 18, the U.S. 14 and Japan has 13.

--Americans Vincent Hancock and Amber English took gold in skeet shooting on Monday. Hancock set an Olympic record with 59 hits against just one miss. Hancock also won gold in the 2008 and 2012 Olympics.

English also set an Olympic record, missing just four shots in the final. She rallied from third position going into the final to claim gold.

In other Olympic news:

--Nishiya Momiji, 13, of Japan won the women's street skateboarding event to become one of the youngest gold medal winners in Olympic history.

--The Russian Olympic Committee captured gold in the men's all-around gymnastics competition.

--Hong Kong's Edgar Cheung captured the city's first gold medal at the summer Olympics in 25 years, winning the fencing event.

--Hidilyn Diaz won the 55kig weightlifting event to give the Philippines its first ever Olympic gold medal.

--Japan took gold in the first-ever mixed doubles event in table tennis.