A 16-year-old boy was grazed in the head when a gunman fired at him outside a Bronx public housing building this week, authorities said Thursday. 

The teen was walking with two friends on Story Avenue, on the grounds of NYCHA’s Monroe Houses in Soundview, when he got into a dispute and a gunman fired multiple times at him, according to cops and police sources. 

The victim, who suffered a graze wound to his head — ran into a building with his friends, surveillance video shows. 

The gunman trailed behind, pointing a gun as he ran, according to the footage.

The teen was able to escape and the alleged shooter — last seen wearing a black hooded sweat jacket, black jeans and white sneakers — was still at large Thursday. 

Nine .40 caliber shell casings were recovered on scene, and one bullet fragment was recovered, the sources said. 

No one else was hurt.