A Brooklyn mother of four found dead inside inside a black plastic bag in a NYCHA apartment building had been chopped up, police said Monday.

The death of Michelle Montgomery, 39, is being investigated as a murder though her cause of death has not yet been determined.

“We found out last night she was chopped up,” a distraught relative who declined to give her name told the Daily News. “Right now everyone is just in shock.”

The discovery was made about 9:35 a.m. Sunday by NYCHA workers in the trash compactor room at a Borinquen Plaza building on Bushwick Ave. near Seigel St. in East Williamsburg. The room is normally kept locked and is off limits to residents, a building worker said.

“We don’t have any information of what happened. We are still in the dark,” the relative said. “She’s a good person. That’s just number one, she’s a really good person.”

“She was a caring and loving mother,” another relative added.

Montgomery lived in the Gowanus Houses, nearly four miles from where she was found dead.

“That was my friend,” said the victim’s next-door neighbor, who declined to give her name. “I knew her since I’ve been in the building, for seven years. She’s funny. It’s just shocking to hear what happened.”

The victim worked for Amazon and “was making valentine baskets, Easter baskets as a side hustle,” the neighbor said.

Residents of Borinquen Plaza were shocked a body was discovered there.

“It’s strange,” said resident Michael Batista, 41. “The building is good. I don’t know. It’s suprising.”

“There’s cameras and it’s a big building,” she added. “They have to find something.”

Rebecca Davila, 57, has been watching her back since the discovery.

“It was scary to go downstairs — you just can’t believe something like that happened in your building,” she said. “In the 15 years I lived here, I never seen anything like that.”

The building where she was found was the scene of a gruesome double murder in 2008 in which a woman was fatally shot by her abusive boyfriend, who was then shot dead shot by the woman’s vengeful father.

With Theodore Parisienne