A stunning fall dropped defending gold medalist Eric Bergoust of the United States from first to last in aerials Tuesday, allowing Ales Valenta of the Czech Republic to win gold.

Hometown favorite Joe Pack, a football and soccer star at nearby Park City High School, won the silver and Alexei Grichin of Belarus won bronze.

Valenta nailed a revolutionary quintuple-twisting, triple backflip on his second jump. It was only the second time he had tried it in competition, and the first time he landed it.

He said landing the quint-twist was "a lucky shot."

"I've done it maybe 10 times on snow," Valenta said. "That's why I was very, very lucky. That's part of the sport. You need luck."

Valenta won with a total score of 257.02 to 251.64 for Pack.

The Czech star said he was more worried about himself than the competition, but most people took for granted that it would take something special to defeat "Air Bergy," the quirky perfectionist who was a heavy favorite to repeat.

Bergoust led all competitors after the first jumps, 130.38 to Valenta's 127.04. He was the final of 12 jumpers in the second round on a cold, windy day at Deer Valley Ski Resort.

It was a loose jump, nothing like what he normally displays, and he landed flat on his back. He stood up, a glazed look of shock painted on his face, while his American coach, Matt Christensen, looked on stunned.

His score was just 88.11, by far the lowest of any jumper.

Bergoust said he took too much speed on the run into the jump, got too much air, over-rotated and probably overdid it because he didn't want to be conservative. He saw Valenta's score and knew he'd need something special to beat it.

"I didn't want to go out and finish fourth," Bergoust said. "I wanted to get the gold or last, and I got last."

It marked the first time Bergoust had finished out of the top 10 in 13 months and only the third time in the last 21/2 years.

When Bergoust fell, Valenta hugged his coaches, knowing his huge gamble had paid off.

Meanwhile, the big Joe Pack cheering section erupted. Their guy took silver after a difficult lead-up to the Olympics, in which he needed a coaches' discretionary pick just to make the U.S. team.

It turned into the classic case of Hometown Boy Makes Good, and Pack said he felt like half the city was in the stands cheering for him.

"It's something that, since I moved here, it's been in the works," Pack said. "I can't describe the feeling of the crowd, how much you feel the energy."

Pack gave the United States its 19th medal of the Olympics, leaving it one short of the goal the United States Olympic Committee set for the games. Three of the medals have come from freestyle -- Shannon Bahrke and Travis Mayer both won silver in moguls.