The incident happened about 11 p.m. at Caliburn Drive near Manchester Avenue.
One of the victims, 37-year-old De Edmond Brown, died at the hospital.
The boy was hit in the chest and was reported in stable condition and was expected to be OK
The third victim, a 31-year-old man, was also expected to be OK.
Police said they found the suspect at the hospital, where he, too, was being treated for gunshot wounds. They said a second suspect was still at large.
Detectives said Brown was socializing with friends when the two suspects approached the group and began firing. The group scattered in different directions. Brown ran inside the apartment complex, where he was tracked down by the suspects in a hallway and shot multiple times in the upper torso, detectives said.
Homicide detectives are handling the case, which is believed to be gang related.