New York City Fire Commissioner Daniel Nigro said Vincent Malveaux was engaged in functional skills training around 10:30 a.m.
Nigro said the 31-year-old from Brooklyn was about three quarters of the way through the course when he started to feel sick and passed out.
An ambulance was on the scene for the training session and Malveaux was immediately taken to Harlem Hospital.
Nigro said Malveaux never regained consciousness and died around 6:30 a.m. Friday with his parents at his bedside.
Malveaux "was doing fabulously" and "was extremely fit," according to the fire commissioner.
The medical examiner will work to determine his exact cause of death.
"We are devastated by his loss, and our entire city grieves together with his family, friends, and colleagues," Mayor Bill de Blasio said.
Malveaux was sworn into the current Probationary Firefighter class on October 25 and was in week six of 18 weeks of training.
Previously, he worked as an Emergency Medical Technician in the Bronx where he responded to thousands of calls for help, including throughout the coronavirus pandemic.
"This is a heartbreaking loss of a young man who chose a life of brave service to others, first providing outstanding emergency medical care as an EMT in the Bronx and then training to be a New York City Firefighter," Fire Commissioner Daniel Nigro said.
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