An innocent bystander was shot in the leg Sunday as a domestic dispute played out in the hallway of her Staten Island building, police said.

The 17-year-old girl heard people arguing in the hallway of the Coursen Pl. building in Stapleton and left her apartment to see what was happening around 2:30 a.m., cops said.

When she walked into the hallway, the teen was struck in the left thigh by the gunman’s bullet.

Police said the shooter pulled out the gun as his brother fought with an ex-girlfriend.

The girl, who was not the intended target, was taken to Richmond University Medical Center in stable condition.

Police arrested the shooter, identified as Jason Dale, 23, and charged him with assault, possession of a weapon and criminal use of a firearm.

Police also took a 49-year-old man in for questioning. Charges against him are pending, officials said.