The fire broke out inside the home on Astor Street at around 4:45 a.m.
Video posted on CitizenApp showed heavy flames shooting from the home.
Firefighters scrambled to get two adults and three children out of the home.
They are being treated for various injuries at University Hospital.
A 7-year-old boy, identified as Sahir Hartfield, did not make it out. His body was located on the third floor by firefighters.
According to the Newark public safety director, the boy's father, who had already escaped the fire, tried to get back into the burning home from the roof of the house next door.
He was helped down from that roof by firefighters.
In all, three families were displaced from three homes that fall under the Newark Housing Authority.
Families from the other units spent Thursday afternoon looking for what of their belongings could be salvaged.
The Essex County Prosecutors Office is conducting the investigation into what sparked the fire.
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