A woman was fatally shot by her ex-boyfriend during a fight at her Bronx apartment, with their 6-year-old son in the next room, authorities said.

Shoshane Rattigan, 28, started arguing with the killer, identified as Tyrone Lowe, at her home on Bogart Avenue in Morris Park shortly before 4 a.m. Tuesday, sources said.

Their 6-year-old son was sleeping in the next room along with the woman’s 20-year-old nephew before they were awakened by the sounds of the couple yelling at each other.

During the fight, the ex pulled out a gun and shot Rattigan in the head, according to police.

When the boy and the other man ran out to see what had happened, they found Rattigan on the floor with a gunshot wound to the head. She was pronounced dead at the scene.

Police said Lowe, 30, then ran out of the building and fled in a silver Honda Odyssey.