The bodies were discovered after her 19-year-old son heard an argument between the two adults, escaped out a window and called authorities.
By the time police arrived moments later, the three were dead. The body of the boyfriend, believed to be about 33 years old, was found in the entry of the first-floor apartment on a quiet, tree-lined street in the Flatlands section of Brooklyn, said chief police spokesman Paul Browne yesterday.
The bodies of the woman and her baby boy were found face up on the bed in her bedroom.
The officer and child were apparently shot in the chest. It's not clear where the man was struck, or how many rounds were fired.
The teenager, who is the officer's son from a previous relationship, was uninjured.
It's not clear what prompted the dispute. Police were still investigating and had blocked off the street as onlookers in the working-class neighborhood clustered nearby.
The officer worked in Queens for at least the past 13 years. She was off-duty at the time.
A next-door neighbor, who identified herself as an aunt, said she could find no reason for the deaths.
She said the officer was always smiling and waving to her, and seemed like a happy person.
"It's terrible," Agnes Samuel, 83, said as she choked up. "For people to take a life like that. Oh, Lord!"