FAMILY HORROR: Dondre Samuel with police yesterday after he clambered out a window while his mother killed two others and herself. (Benny J. Stumbo)
An NYPD cop yesterday killed her boyfriend, their 1-year-old son and then herself in their Brooklyn apartment, police said.
Officer Rosette Samuel, 43, left a note saying she was “sorry” for murdering younger lover Dason Peters, 33, and their baby boy, Dylan, after a weekend of arguing — but said she “had to do it,” sources told The Post.
The 13-year NYPD veteran added that she killed Dylan because “she didn’t want to go it alone,’’ a source said.
Samuel shot Peters as he tried to flee, leaving his body near the front door. She then shot the baby in the chest and killed herself. She and the baby were found next to each other in bed.
“My son is my heart! My son is my everything!” wailed Peters’ grief-wracked mom, Rosamund Peters, as she rushed to the first-floor apartment at 807 E. 56th St. in Flatlands. “Oh, my God! What a loving son I have!”
The killings came three months after Samuel — who had spent years in the Manhattan Traffic division — was transferred to the 108th Precinct in Queens and docked 20 vacation days for failing to show up for traffic court, which led to the dismissals of nearly two dozen tickets.
Yesterday’s tragedy was set in motion Saturday, when Samuel received a letter about her and Peters, a track-maintenance supervisor for the MTA, a source said.
The note — which was found torn up in the toilet — sparked arguments between Samuel and Peters, sources said.
Her 19-year-old son from a prior relationship, Dondre Samuel, scrambled out through a back window during the shootings, wearing only shorts and a windbreaker.
“He was shaken up,” said witness Anthony Beckford, 19. “My uncle asked what happened . . . He was all scraped up and he ran into the back yard. His elbows and his knees were scraped. He said, ‘Look, look!’
“He was frantic. He couldn’t really talk,” Beckford said.
Dondre called 911 — bringing cops racing to the apartment.
“We’re devastated right now,” said a cop at Manhattan Transit. “[Samuel] was a lovely person. She was funny, a great personality, outgoing. She’d always talk about her family . . . She was very fond of her children. They were her life.”
Peters’ cousin, who declined to give his name, said Peters “was a loving father. He loved his child. He was a very good father. They were very close.”
Asked if Peters and Samuel had prior domestic strife, the cousin said, “Never.”
Additional reporting by Lorena Mongelli, Jessica Simeone, Wilson Dizard, Lisa Hagen and Lia Eustachewich