The incident happened in Stapleton while the unit was returning to quarters from a call.
According to police, the FDNY fire truck was traveling eastbound on Broad Street when it struck the 7-year-old boy as he was crossing the street just before 7:30 Saturday morning.
Firefighters immediately stopped and treated the child before medics arrived.
Authorities say the child was by himself at the time, but were able to locate his family and notify them about the crash.
The child was taken to Richmond University Medical Center in critical condition.
The boy was later moved to Cohen's Children's Hospital.
Police are investigating why the boy was left unsupervised.
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