A man was found fatally shot in his Brooklyn apartment Sunday evening — just two days after his next-door neighbor was mysteriously shot dead in her unit, cops said.

The 54-year-old man was discovered by his sister inside his fifth-floor apartment in the Bushwick Houses on Moore Street around 5 p.m. Sunday, cops said.

“[The sister] hadn’t heard from him and went to check up on him and found him shot dead,” said a police source, noting that he’d been shot one time in the head.

Authorities are withholding his identity pending notification of his family.

The death came just two days after the man’s neighbor, Ana Devalle, was found bound by her hands and shot in the back of the head in her unit.

The 62-year-old Devalle was found in the next apartment over around 6:45 p.m. Friday.

Investigators haven’t announced a suspect in either death.