A man and woman were fatally stabbed in Brooklyn Saturday night, and cops took their son into custody as a person of interest, police sources said.

Cops responding to a 911 call for an assault arrived to the apartment building on 45th St. near 12th Ave. in Borough Park at about 5:20 p.m. to find Hatzolah medics removing the wounded 75-year-old man and 75-year-old woman, cops said.

Medics rushed the victims, who both had stab wounds about their bodies, to Maimonides Medical Center where they were pronounced dead, cops said.

The victims’ 46-year-old son barricaded himself for over an hour inside the family’s second floor apartment before giving himself up to cops, police sources said.

The son was taken into custody as a person of interest, the sources said. Charges were still pending late Saturday.

Neighbors mourned the well-liked victims, and said their block is quiet and crime-free.

“They were special people,” neighbor Schmiel Weiss said of the victims. “It’s unfortunate that this is how their life had to end, but we don’t know God’s plans.”

“I feel like this is a real real big tragedy. This never happens here,” said a 17-year-old neighbor, who wished to remain anonymous. “I was shocked. We are all in big shock.”