A brave Queens mom threw herself over her disabled stepdaughter in a desperate, but doomed, effort to save the younger woman from a rampaging nephew, who was arrested Saturday for fatally stabbing both women and a second aunt, sources said.

The accused killer was smoking weed in the kitchen of the 182nd Street home in Queens when he got into an argument with one of the women and allegedly snapped, sources told The Post.

During the attack, Hyacinth Brown-Johnson, 65, threw herself over her bedridden step-daughter, Patrice Johnson, in a last ditch effort to protect the disabled 26-year-old, but both were ultimately killed. 

“I heard they found Hyacinth hovering over Patrice in her bedroom like she was protecting her.  Hyacinth had a lot of defensive wounds. She was fighting for Patrice and herself,” a family friend told The Post. “It’s heart wrenching. It’s like putting a dagger in the heart.” 

Brown-Johnson’s daughter, Latoya Gordon, 47, was also found dead in the home alongside her mother and Johnson. They were discovered by Brown-Johnson’s son and a home health aid, authorities said. 

The building’s landlord, Patrick Ogbedor, 62, told The Post he heard a scuffle take place between 2:30 a.m. and 3:30 a.m. before he heard a car drive away. 

The suspect then stole Hyacinth’s 2004 Toyota Sienna and drove to Virginia after the bloody Friday homicides in Springfield Gardens, sources added.

Video recovered by police appeared to show the car speeding just before 5 a.m. Saturday. With the surveillance footage in hand, the NYPD put out an alert on the stolen car.

Virginia state police later spotted the Toyota in Prince George. The car had run out of gas, and approaching officers found the driver behind the wheel, covered in blood and with wounds on his hands, sources said.

The driver later allegedly incriminated himself, describing how he’d attacked each of the women, the source added.

He was taken to a hospital and is awaiting extradition, the source said. 

The victims’ home was surrounded by police tape early Saturday, with an NYPD patrol car sitting out front.

An NYPD spokeswoman could not immediately confirm the details of the arrest, saying “charges were pending.”

Peter Wolf, who had been Patrice Johnson’s guardian since 2005, said that she had been disabled since birth and unable to speak or dress herself. 

Patrice Johnson’s biological mother died of lupus when her daughter was a child, and Patrice’s father, Milton Johnson, later married Hyacinth — who pledged to care for the girl and not put her in a nursing home, the family friend said.

“She really loved this child,” the friend said of Hyacinth.

A neighbor said Hyacinth lived in the Queens apartment for at least 15 years before her daughter and son recently moved in with her. 

Up until then, the neighbor said he thought Hyacinth lived alone because she was the only one he saw going to and from the apartment. 

“I have not seen the [step-daughter] for years now. I didn’t think she was still there,” the neighbor said. “I don’t even want to go outside. I don’t want to see the house. It is so sad.”

Additional reporting by Dean Balsamini and Valentina Jaramillo