Medics tried but were unable to revive Samuel Fisher, 24, who was rushed to Stamford Hospital, where he was declared dead, the Advocate said.
Fisher, a recent Harvard graduate and native of Newton, Mass., took part in the event with several co-workers to benefit Greenwich-based Kids in Crisis, the Advocate said.
The triathlon included a nine-tenths of a mile swim, 24.8-mile bike ride an d 6.2-mile run, according to its website.
An autopsy will be conducted to determine the cause of death, the Stamford Advocate said.
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