A young woman believed to be pregnant with her second child was killed along with her boyfriend after a gunman opened fire on the couple early yesterday in a courtyard at a Sheepshead Bay housing project.

The bullets began flying about 5 a.m. at the Sheepshead Bay Houses on Avenue W near Nostrand Avenue, police said.

Crystal Sweet, 22, was shot three times in the head and neck and pronounced dead at the scene, police said. Her boyfriend, Timothy Walter, who had a long rap sheet, also was shot and killed.

A third victim, a 30-year-old man believed to be Walter’s brother, was taken to Kings County Hospital, where he was listed in critical condition.

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Cops were still trying to determine a motive for the bloody attack and sort out whether all the victims were intended targets.

“It was hard for me when they took the body,” said Sweet’s distraught mother, Josephine Rodriguez. “I wanted to run and say, ‘Crystal, Crystal, I’m there for you!’ It’s so hard. I couldn’t tell her I loved her. I couldn’t say goodbye.”

Sweet’s mom said her daughter had been working as a home health worker and wanted to help handicapped children.

Sweet, who has a 5-year-old daughter, Lydia, had told her mom several weeks ago that she thought she was pregnant. The mom bought her daughter a home pregnancy test but never learned the results.

But Rodriguez said several of her daughter’s friends told her that Sweet had confided to them she was pregnant.

“Whoever has not lost a child does not know how I feel,” Rodriguez said. “She was outgoing. She loved going to places. She was a wonderful daughter, a beautiful mom. She’d do anything for anybody. She was a wonderful person.”

Sweet, Walter and the third victim were coming home from a party when the shots rang out.

Sweet’s family said they heard the shooting may have stemmed from an earlier altercation between Walter and some other people. Walter had at least 24 arrests on his record, including two for murder and weapons possession and drugs.

“He was bad news,” said Sweet’s grandmother, Petra Kopelaki. “I kept telling her to leave him. She wouldn’t.”

The wounded man has 13 arrests on his record.

Sweet’s father, Ricardo Rodriguez, 49, called his daughter “an awesome person.”

“You don’t come into contact with very many people like her. She was just so pure of heart. She always had a smile on her face, so full of energy and joy. That’s my daughter. The sweetest person you’ve ever met,” the grieving dad said.

Additional reporting by Perry Chiaramonte, Reuven Fenton and Larry Celona

john.doyle@nypost.com