The fire department says that Ladder 111 was responding, with lights and sirens on, to a fire at Nostrand Avenue and Quincy Street when the accident happened around 4:10 p.m.
The truck went through the intersection at Monroe Street and Marcy Avenue and collided with the motorcyclist, who was thrown into the side of a nearby building.
Reginald Brown, 46, of Brooklyn was taken to Woodhull Hospital, where he was pronounced dead on arrival.
Brown was a graduate of The Doe Fund's Ready, Willing and Able program. He ended up working for the organization, which helps homeless people in New York City, for the last 10 years.
Meanwhile, police have arrested 17-year-old Kevin Saunders for allegedly starting the fire on Nostrand Avenue. Authorities say Saunders was playing with fireworks, and one of them sparked a fire in rubbish near the building.
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