Police on Thursday arrested a 17-year-old and charged him in the fatal shooting of a man in September at the Potomac Gardens apartment complex near Barracks Row in Southeast Washington.

Quincy Garvin, of Southeast, has been charged as an adult with first-degree murder while armed.

He is the second person arrested in the slaying. On Oct. 26, Saquan Williams, 16, of Southeast was also charged as an adult with first-degree murder.

The suspects are charged in the Sept. 10 shooting of Carl Hardy, 24, of Northeast. He was shot about 6 p.m. in the 1200 block of I Street SE. Police said he died at a hospital on Oct. 1. He was found lying between two trash bins.

According to an arrest affidavit filed in the case against Williams, Hardy was found wounded in a courtyard of the gated complex. Police said they found 16 shell casings associated with assault-style rifles, and another nine casings of 9mm ammunition from a handgun.

Police said in the affidavit that the shooting was sparked by a dispute between two neighborhood crews — one in Potomac Gardens, of which Hardy was a member — and another in Wellington Park, two miles to the south and east of the Anacostia.

The affidavit says that one of the suspects does not live in Wellington Park but frequents the neighborhood, and that police found pictures of him on Instagram holding a rifle that resembles an AK-47 and two handguns.

Police said they believe Williams bragged about the shooting on Instagram posts two days after Hardy was wounded. In one post, police said he warned people to stay off his turf. Another, according to the affidavit, said: "He Was Tuff Til I Ran Down Widd With Both Glizzy's." Police said "Glizzy" is street slang for a Glock handgun.

The affidavit says that they seized a 9mm handgun from Williams at his house and that it matched several of the shell casings found at the Potomac Gardens shooting scene.