The victims were pulled from the inside of a home on Agar Place after it went up in flames around 3:15 a.m.
The lone survivor was the woman's daughter, who was also injured.
"We feel really so bad for her because she was such a nice lady," neighbor Judy Delvecchio said. "She didn't deserve that."
Video from NewsCopter7 showed heavy damage to the middle of the structure.
"She was a good woman, she didn't bother anybody," Delvecchio said. "She tried her best to hold her family together. Very sad."
Both victims who died sustained severe smoke inhalation, authorities said, and the single-family home was gutted.
"Firefighters were met at the door with heavy smoke condition," Hackensack Fire Chief Carmine Maceri said. "And until we were able to get a line into place, we were unable to get into that house because of the extreme heat that was coming out of that home."
Firefighters say it took about 20 minutes to knock the flames back before they could gain entry.
"We located one female victim, who is a fatality at this time," Maceri said. "A second male victim was also located shortly after that."
Investigators said all three victims were in the rear of the home, and the third was being treated at Hackensack University Medical Center.
"When I heard who it was, we were shocked, we were saddened," local store owner Tony Competiello said. "It's an older lady, not as mobile...I'm sure the old-time Italian community is really going to feel it, because these are people who came here and worked hard their whole lives, and there's a bond there."
Neighbors said the elderly father lived in the home as well but worked overnights and was not at home at the time.
"Obviously we are a real small town," South Hackensack police Deputy Chief Robert Chinchar said. "Everybody knows everybody. So something like this really hits home to everybody. It's going to take a while to recover from this, but we will get through it."
The cause of the fire is under investigation.
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