McKayla Maroney's feet skidded out from under her, and a look of shock crossed her face.
The Olympic gold medal that everyone was certain was hers was gone.
The world champion's rare mistake opened the door for Romania's Sandra Izbasa, and she took advantage of it Sunday, winning the title on vault. Maroney claimed the silver medal and looked downright surly as she stood on the medals podium.
Russia's Maria Paseka won the bronze.
Earlier Sunday, Zou Kai won his fifth career gold medal, defending his title on floor exercise. He already had one gold from China's victory in the men's team competition last week, and he has three more from the Beijing Games. He has a chance to duplicate his Beijing trifecta on Tuesday, when he tries to defend his Olympic title on high bar.
Maroney was considered all but a lock for the gold medal, which would have given the US women three in the first three individual gymnastics events. She won her world title last year by almost a half-point and topped qualifying in London by a similar margin. She was so impressive Tuesday night in the team final that US coach John Geddert suggested they rename her vault "The Maroney."
"Man, that thing is beast!" all-around champion Gabby Douglas said earlier Sunday. "How she gets so high, I'm so amazed. When she does it at camp, the table literally shakes."
Her first vault was the Amanar -- a roundoff onto the takeoff board, back handspring onto the table and 2.5 twisting somersaults before landing -- and she did it better than the woman for whom it's named. She got such great height off the table the folks in the first few rows had to look up to see her, and her form was perfect in the air, legs pencil-straight, body tightly coiled.
She took a hop on her landing, and came down out of bounds. But even with that 0.3 deduction, she still scored 15.866, including a whopping 9.666 for execution.
Another vault like that, and the gold was hers.
But she appeared to land the second one on the back of her heels. Her feet slid forward and she dropped to the mat with a loud "plop!" The crowd gasped, and Maroney looked stunned. She's as consistent as a Swiss watch on vault, never making errors in training or in competition.
She scored only a 14.3, giving her an average of 15.083. Coach Arthur Akopyan tried to console her, but Maroney simply stared straight ahead, knowing her chance to add an individual gold to the one she won with the Fierce Five was gone.