The attack happened in a home on East 18th Street off Gravesend Neck Road.
Police say shortly before 8:00 Friday night, the ex-husband of a woman who lived in the home went inside armed with knife in hand and in a fit of rage. He stabbed three women and his wife's 4-year-old nephew.
Across the street from the home a group of mechanics from an auto body shop heard the tragedy unfold, and neighbors say they rushed to help the victims.
"A woman came running out of the house, they ran across, she pulled them into the house," said one neighbor.
Police said one woman suffered multiple stab wounds to her face and torso and was rushed to Coney Island Hospital where she died. She has been identified as 29-year-old Jie Mei.
The other victims included a 38-year-old woman stabbed in the leg, a 62-year-old woman stabbed in the torso and a boy slashed in the shoulder.
All were listed in stable condition at area hospitals.
Han Min Pan, 45, was arrested a few blocks from the crime scene. He was charged with murder, attempted murder and related charges.
What provoked the confrontation remained under investigation.