Two Brooklyn sisters were shot, one critically, by a raging ex-boyfriend who opened fire on them inside a Brooklyn apartment, police said Friday.

Police were searching for the ex, who left the Fulton St. apartment building near Utica Ave. in Bedford Stuyvesant following the 10:30 p.m. shooting Thursday.

The gunman remained at large Friday.

Neighbors heard multiple shots and called police, who found a 21-year-old woman riddled with bullets, cops said. The woman’s older sister, 40, was also at the scene, with a gunshot wound to the stomach.

EMS raced both victims to Kings County Hospital, where the younger sibling was listed in critical condition. The older sister was treated and expected to survive.

Cops quickly identified the shooter as the younger sister’s ex-boyfriend.

Detectives on Friday were scouring the area looking for surveillance footage that can help track him down.