The incident took place around 3:40 p.m. Sunday at the Villages at Berkley housing development on Berkley Road.
Authorities say 45-year-old Michael Targett shot 52-year-old Stephen Newcomb multiple times at the foot of a stairway in Newcomb's upper-level condominium.
Afterward, Targett returned briefly to his pickup truck, then walked to the side of the 1074 Tristram Circle unit and shot himself in the head with a .357 Magnum handgun.
An investigation by the Mantua Township police and the Gloucester County Prosecutor's Office determined Targett's estranged wife was living with Newcomb. She was not at home at the time of the shooting.
An investigation by the township police department and the GCPO is continuing.