A 23-year-old woman fatally stabbed her mother and then killed herself Saturday in a brownstone in leafy Park Slope — the second-murder suicide in the building in two years, law-enforcement sources said.

Police responded to 386 Second St. in the trendy Brooklyn neighborhood after a 911 call about an unresponsive woman at the scene shortly before 8 p.m. and found a 59-year-old woman with multiple stab wounds, according to the NYPD.

Cops searched the home and then found the younger woman, also with stab wounds, who was identified as the older victim’s daughter, police said.

Both women were pronounced dead at the scene by EMS.

The younger woman is believed to have gotten into a nasty spat with her live-in mother and killed her before turning the knife on herself, sources said.

The two women have not been officially identified.

The address was the same location where Jason Jackson and his partner, Olga Kirshenbaum, both 34, were found shot to death in January 2024 in what police said was a murder-suicide.

Police believe Jackson, a cook, shot Kirshenbaum, a prominent financial consultant known as “The Money Whisperer,” before turning the gun on himself.

Longtime neighborhood resident and illustrator Fred Fassberger told The Post that after the 2024 murder-suicide, locals held emergency community meetings at a nearby church.

“That was the magnitude of an incident like that, that the community wanted to get together and know what was going on,” he said Saturday.

Additional reporting by Larry Celona