It was not immediately clear what sparked the incident, which occurred around 5 a.m. in the area of Florida and Beach avenues.
Atlantic County Prosecutor Ted Housel said 29-year-old Shamir Harper was shot twice by 24-year-old Naheen Hogans-Henderson.
Police responding to reports of shots fired soon saw the gunman running on the boardwalk toward the beach, and he then shot himself once in the head. He was pronounced dead at the scene.
Meanwhile, Harper ran off and flagged down a passing motorist who took him to the hospital. His wounds were not considered life threatening.