A scorned ex shot his former girlfriend dead, critically wounded her new boyfriend, then fatally turned the gun on himself inside a Brooklyn apartment Sunday — the third murder-suicide in the city in five days, police and sources told The Post.

Darnell Solomon, 30, opened fire in an apartment on Utica Avenue near Avenue M in Flatlands, first striking his ex-girlfriend Jened Duncan, 24, in the head, according to cops.

He then blasted the woman’s new flame, 33, in the torso, before shooting himself in the head, investigators said.

None of the parties in the bloodbath, which took place just after 2 p.m., was immediately named.

Duncan and Solomon were both found by authorities clinging to life, but succumbed to their wounds at Mount Sinai Hospital and NYC Health + Hospitals, respectively, cops said.

The current boyfriend was rushed to Brookdale Hospital, where he’s listed in critical but stable condition, according to officials.

A man at the scene who said he was Duncan’s uncle said his wife became distraught when she was had trouble getting their niece on the phone this afternoon.

“My wife was panicking,” said the uncle, who declined to give his name. “She kept saying that she couldn’t get in touch with her, that she wasn’t picking up her phone calls.

“She was a good kid, a very good kid, never got in trouble … We’re just trying to figure out why would somebody do this. It’s just too painful.”

A woman who identified herself as the aunt said the slain woman was an aspiring teacher.

“I just gotta think positive because I have kids to live for, her sister lives with me,” said the aunt, who also declined to give her name. “I’m just going to hold it together. I can’t bring her back. She’s already gone.”

The incident is the third murder-suicide to shake the city in less than five days.

Late Wednesday, Yonathan Tedla beheaded his humanitarian wife, fatally slit the throat of their 5-year-old daughter then hanged himself in the family’s tony Harlem brownstone, authorities have said.

The 46-year-old Columbia University computer tech was in the midst of a highly-contentious divorce from wife Jennifer Schlecht, 42, her father has told The Post.

On Friday night, Dineshwar Budhidat fatally stabbed wife Donne Dojoy, 27, inside their Queens home — purportedly in a jealous rage over her infatuation with a hunky Bollywood star.

Budhidat, 33, then hanged himself from a tree in a wooded area not far from their Ozone Park home.