A deranged Bronx man fatally gunned down three members of his family — inclduing his elderly, “Golden Girl” mother — inside a city housing project Wednesday morning before shooting himself to death, law enforcement sources said.

The 44-year-old killer, who was due in court on a gun rap later in the day, blasted his 75-year-old mother, his daughter and her boyfriend in a horrific massacre at Castle Hill Houses around 9:45 a.m., police and sources said.

Stunned tenants said the elderly victim — identified by neighbors and sources as Theresa Stukes — was a fixture in the building known as a beloved member of the community.

“I started crying, because that’s one of the ‘Golden Girls,'” neighbor Jeanette Martinez, 48, told The Post. “She was always out doing celebrations, barbecues, supporting people, giving good advice. She was a wonderful person.”

Police have not said what may have triggered the bloodbath.

Stuke’s body was found near the rear of the apartment near a bedroom, not far from the suspected killer’s 26-year-old daughter, the sources said. 

The younger woman’s beau was found near the front door.

Video reviewed by investigators shows the suspect stepping outside much earlier — around 8:10 a.m. — and leaving a voicemail to his 20-year-old son who lives in North Carolina, sources said.

He went back inside five minutes later and was discovered on the couch with a gun in his hand, the sources said.

The bodies were found when the mother of the gunman’s child called the cops asking for a wellness check, according to the sources.

None of the victims have been officially identified by police.

Family friend Janet Dukes said Stukes had often stood by her troubled son.

“She went to bat for him in the way a mother does,” said Dukes, 63. “Whatever happens, the son has to go to prison, lose jobs, parents are there. She stuck with him 100% in every kind of way.

“He had a big mouth,” she said. “He always talked, he had fun. But you would never have thought this would happen. He wasn’t that kind of person. There had to be something else that went through his mind.”

Others remembered the victims fondly.

“It was an amazing family,” 38-year-old tenant Luis Rolon said. “I just found out this morning and it’s devastating to hear about it.

“It’s just heartbreaking,” he said. “I saw her literally last week. I can’t imagine what everyone else is going through in the family.”

Another neighbor, Margarita Rivera, 70, described the suspected gunman as “a typical young man with problems.”

Rivera said she had known the slain mother for 49 years, and they were once neighbors on the 11th floor for years.

“Theresa was one of the nicest people in the building,” she said. “She made the best collard greens for my husband, even when he was in the hospital dying. 

“When I got home and found out about this this afternoon, it was just very overwhelming,” she added. “I can’t take it. It’s too much.”

The city medical examiner will make an official ruling on their causes of death.