Gunfire erupted in Coney Island early Sunday, leaving a bystander shot in the back, police said.

A man and a woman were arguing on a residential block of West 16th Street when one of them pulled out a pistol at about 4:30 a.m., police sources said.

The person who pulled the gun fired one round, hitting a 38-year-old man in the back, the sources said. The man, who had been standing nearby next to his car, was taken to Coney Island Hospital. He was expected to survive.

“It is believed at this time that the victim was not the intended target,” a police source said.