Melvin Coronado, an attendee, was recording the beginning of the women's finale of the Red Hook Criterium when he said one of the cyclists fell into the path of the other competitors.
The cyclist's bike may have collided with a traffic cone or camera mount, Coronado said.
The crash created a domino effect: Others fell from their bikes, and several landed in a massive pileup involving about two dozen riders.
** Watch the pileup occur in the video player above **
"(The Red Hook Criterium) is one of the most dangerous cycling races," Coronado said.
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