Police did not identify which of the men had been shot.
The incident occurred shortly before 2 p.m. when police said two men approached the victim in the 500 block of H Street NE, blocked his path and made statements indicating a possible robbery.
An arrest affidavit filed in D.C. Superior Court says one of the men was armed with a handgun with an extended magazine, and the other man held his hand under his shirt as if he had a firearm.
The victim told police he tried to walk away but was again blocked by one of the men who said, “Don’t move,” the affidavit says.
Police said the intended victim “brandished his lawfully possessed firearm and shot at the suspect, striking him in the arm.” Police said they recovered 10 bullet casings.
A police report made public on Wednesday says the windows of four businesses on the H Street commercial strip were damaged — two restaurants, a clothing store and a cash express shop.
Police said the man who fired his gun called 911.
In October 2017, the U.S. Court of Appeals for the D.C. Circuit struck down a key provision of the city law that had required residents to show a “good reason” to carry a firearm outside the home.
Since then, D.C. police said 4,448 people have applied for a conceal carry license, and 3,387 have been approved. Shootings involving a person with a legal gun in the District remain rare.
Police said they are still investigating the circumstances surrounding the shooting to determine if it was justified.
The man who fired the gun could not be reached for comment on Wednesday.
Correction: An earlier version of this story mistakenly said the man who fired had a gun with an extended magazine.