The fire broke out in the 1st-floor apartment around 1:30 a.m. on Sunday.
Authorities say a group of people on Nagle Avenue and Dyckman Street lit fireworks on the sidewalk outside of a building.
At least one of the projectiles came through a window and set a couch on fire inside the apartment.
It is the same couch where the grandmother usually sleeps.
Four generations of the family lived in the home together. Fortunately the family was not home at the time of the incident, but a brave neighbor had to rescue their trapped dog.
The dog survived, but the apartment, where the family has lived for over 40 years, is a complete loss.
Eyewitness News reached out to the family but they were understandably too upset to speak.
Friends are now trying to raise money for the now-homeless family.
The incident is under investigation by the FDNY fire marshal and the NYPD Detective Squad.
Mayor Bill de Blasio says police have made more than 200 arrests for illegally selling fireworks.
RELATED | Fireworks explode in hands of men trying to protect kids in Queens
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