JERSEY CITY, N.J. (CBSNewYork) -- Two children are dead following a devastating fire in Jersey City.
Authorities believe an 11-year-old girl was attempting to rescue her 8-month-old brother when they were both killed.
"I'm just sad, my heart hurts, even if I don't know them. I'm sorry," neighbor Lawrence Anderson told CBS2's John Dias. "I just feel so bad for the family. So I just pray for the children."
WATCH: Jersey City Officials Discuss Fatal Overnight Fire
Firefighters responded at around 11:30 p.m. Wednesday. Cellphone video shows smoke billowing from the roof at 470 Martin Luther King Drive as police, who had been nearby, try to gain entry into the burning apartment, CBS2's Alice Gainer reported.
Neighbors said the flames quickly swallowed the home, and they tried their hardest to evacuate.
"Definitely when it happened, I was in shock. When they told us to get out, I couldn't find anything. I couldn't put anything on. I forgot where everything was," one woman said.
Jersey City Mayor Steven Fulop said the children's mother escaped with a 6-year-old boy, and the door locked behind them.
"Police were able to get the front door open in an attempt to rescue the people inside. It was too hot, too much fire. They couldn't get in without any protective gear," Fire Chief Steven McGill said.
Officials said the 11-year-old girl tried to save the 8-month-old boy, who was sleeping upstairs. Her body was found in a hallway, and the boy was pronounced dead at the hospital.
"There's a lot of fire in that ground floor. It went directly up those stairs and into the hallway. Although there was not a lot of fire on the upper floor, it was probably 1200 degrees up there, which nobody would've survived," McGill said.
Web Extra: GoFundMe Set Up To Help Family
Neighbors, who identified the mother and children in Facebook photos, were crushed.
"They were together all the time ... all the time," Michelle Bey said. "She was a good girl. You know, most kids they be out here in the street, they want to do this, but she was a little homebody girl."
"Ain't no words. Kids, man. This is a real tragedy," neighbor Fred Washington added.
As for the cause fire, officials said it was not suspicious and does not look criminal, though it remains under investigation.
Residents who were evacuated were eventually allowed back in.
Three police officers were also hospitalized and treated for smoke inhalation.
CBS2's Alice Gainer contributed to this report
for more features.