Rookie Ken Roczen of Murrieta won the season-opening supercross race at Angel Stadium on Saturday night.
"This is insane, I can't believe it," Roczen, 19, said after winning his first race in the Monster Energy AMA Supercross Series. Supercross is the stadium version of off-road motorcycle racing, or motocross.
James Stewart, a two-time series champion, was just about to pass Roczen for the lead on the 16th lap of the 20-lap main event when Stewart lost control of his Suzuki and crashed.
After getting up from the dirt track, a frustrated Stewart slammed his hands on the seat of his bike and walked away. He finished 17th.