A 21-year-old man was fatally shot inside a Brooklyn housing complex on Monday night, police said.

The victim was found by cops about 9:30 p.m. with multiple gunshot wounds to his chest in the 13th floor hallway of Brownsville’s Tilden Houses at 330 Dumont Avenue, law enforcement sources said.

He was pronounced dead on scene.

Before the fatal shooting an argument ensued between the victim, who lives on the floor he was found, and occupants of a nearby apartment unit, sources said.

Investigators recovered a gun outside of the building, below one of the apartments, sources said.

At least seven people were taken into custody for questioning. No arrests had been made on Monday night.