The horrific deaths of a Brooklyn mom and her 14-year-old daughter who were found slashed next to the family dog at their home may have been a murder-suicide, law-enforcement sources said Tuesday.

The bodies of 37-year-old Azalea Rivas and her teen daughter Azaria were discovered around 4:30 p.m. Monday when the woman’s worried ex-boyfriend broke down the door and found the grisly scene, cops and law enforcement sources told The Post.

The teenager was stabbed once in the back, but it was blunt force trauma to her head that was believed to have killed her, police officials said Tuesday.

She was found with a bag over her head, “probably to contain the blood and the splatter,” Chief of Detectives Joseph Kenny told reporters. 

Authorities said Rivas had died of a puncture to her lung, and also had knife wounds on her wrists and neck that appeared to be self-inflicted.

The body of the small dog, named Biscuit, was found next to the girl, also with a bag over its head, cops said. 

Detectives and the city’s Medical Examiner’s Office have not made an official determination on the deaths, but police sources said they are eyeing the shocking case as a murder-suicide.

The mom’s ex-beau was questioned by cops but is not believed to be a suspect, sources said.

“He actually gained entry to the apartment by breaking in the door,” Kenny said of the ex-boyfriend, who knew Rivas since high school and had remained friends with her.

The man also “removed the bag from [the teen’s head] to check her vitals and saw she was dead,” the chief added.

Police had been dispatched to the scene on Friday after a neighbor reported a possible family dispute shortly before 7:30 a.m. – but cops left when no one answered the door.

“I told the cops I thought someone was getting killed upstairs,” neighbor Steve Schor, who made the Friday call to cops, told The Post Tuesday. “They said there was music playing, and they attempted to knock. Nobody was at the door, so they left.”

“We heard whining, banging, screaming, dog in distress. The dog was the last to go. Then all the noise just stopped.”

On Monday, Rivas’ ex-boyfriend – after not being able to reach the family over the weekend – broke into the apartment and found the gruesome scene, sources said. 

Rivas suffered a brain injury when she and her daughter were run over by a van in New Jersey back in 2016, and had become increasingly erratic and paranoid in the years since, according to police and her uncle, Wilfredo Crespo.

“After the accident, everything changed. We saw physical things, outward. Slurred speech, confusion.“ Crespo told The Post on Tuesday. “After COVID, things took a turn for the worse… Little signs of paranoia. Conspiracy theories. She felt like something was out to get her.”

Even her young daughter “knew that something was wrong,” Crespo said. “She would ask her aunt and her grandmother, ‘Take me home. Let me stay with you.’ … Azaria was very vocal about what was going on.”

He said that Rivas’ mother, his sister, had tried to get protection for the girl, even involving a social worker at her school and contacting child protective services.

“There is a reason why this happened. There are multiple protections we tried to exercise, and no one listened,” Crespo said. “My sister has been fighting for two or three years now. She has been talking to school officials. There’s tons of people who know about this, who knew something was going on. We sought help, but they failed us. They failed her.”

Before the accident, Rivas was a hard worker and devoted parent, trying to make a career in the restaurant industry, Crespo said. 

“She was never a troubled girl, ever,” he recalled. “My sister raised her in the best way possible. In 2021, 2022 she was getting into the restaurant business, Azaria came along, and she was still doing her thing, trying to make her place in the world. She was a hustler. She never, never, never, never showed a violent side.”

An online fundraiser was set up to help the family pay for funeral expenses.

“On Monday September 25, 2023, our family found out the most devastating news that we would ever experience in our lifetime. My niece Azaria and sister Azalea were both found dead in their apartment along with their dog Biscuit,” wrote the GoFundMe page’s organizer, Milina Cayon.

“This is an event we could not have been prepared for. From my family, we ask that you are kind as we are grieving deeply for the loss of our loved ones.”

Additional reporting by Larry Celona and Jorge Fitz-Gibbon