Flames broke out shortly after 2 p.m. in the first floor unit at the 16-story Marlboro Houses on West 11th Street in the Gravesend section.
CeFaan Kim was live at the scene:
Fire officials say eight people were injured - five from one family in the apartment and three were neighbors in the building who were visiting.
The four children injured range in age from nine months to nine years old. Two of those kids are in critical condition. Two other victims were seriously hurt, and four suffered minor injuries.
Neighbors felt helpless until firefighters arrived.
"It was terrifying because we couldn't do nothing because the bars were on the window. We couldn't get the bars off. And we just heard them in there screaming," says Glenda Reyes.
Reyes said the mother tried to run back inside, but then fainted in her arms. Meanwhile, the witnesses say the children's father kept running back in and out to try to save his kids before he eventually passed out.
"He was just in shock. He was shaking - his whole body was shaking. He was covered in all charcoal smoke, he couldn't breathe right," says Omar Yousof.
No firefighters were injured.
An air conditioner used by the family to regulate the temperature of the apartment is believed to have accidentally sparked the fire.
Fire officials say there was an operational smoke detector in the apartment.