The suspect and victim reportedly began to argue in an alley in the 300 block of 32nd Street at 4:50 a.m. Sunday when a shotgun was pulled.
"One accused the other of being a snitch," Draper said. "[The victim] was shot at a fairly close range."
The shotgun blast injured the victim's right arm. He underwent surgery at McKay-Dee Hospital, but his condition was not known.
Police have yet to find the shotgun used in the shooting, but recovered shotgun shells near the scene.
It is unclear whether they were related to the shooting, Draper said.
The incident was the city's second gang-related shooting in four days, but police do not believe the two are related, he said.
On Wednesday afternoon, two brothers, a 26- and 24-year-old, were shot in their older-model Cadillac in the 400 block of Canyon Road. The brothers drove to the intersection of 20th Street and Monroe Boulevard before stopping for paramedics.
The 24-year-old victim suffered minor injuries to the back. His brother was shot in the forehead and was listed in critical condition at McKay-Dee Hospital.
Police arrested Jeremy Gallegos, 19, in connection with that shooting and are looking for a 17-year-old suspect who is also believed to have been involved.