It happened in the 400 block of John B. Carter Road, police believe at an "after hours club."
Investigators say two men and one woman were taken by ambulance to Cape Fear Valley Medical Center for treatment.
Officers say they were found in a personal vehicle that was parked alongside Sunnyside School Road and John B. Carter Road.
The names of the victims have not been released pending notification of next of kin.
The three victims at Cape Fear are in serious condition. Authorities confirmed a fourth victim Monday afternoon and that person is at Chapel Hill Hospitals in serious condition.
Cumberland County Sheriff's detectives are drawing up arrest warrants for a suspect, but are not releasing any suspect information at this time.
On Sunday, detectives were working to uncover more details about how the victims were shot and to determine the location of the shooting.
Anyone with information is asked to contact to the Cumberland County Sheriff's Office at (910) 323-1500.