A shooting in Prospect Hill, North Carolina, killed at least three people on 5 August.
The dead included the suspected gunman, and another person was wounded and taken to a hospital.
The North Carolina State Bureau of Investigation confirmed the incident and said officers responded to an emergency call before 8 a.m. local time.
The state bureau said officers found multiple gunshot victims at the scene, that one victim was sent to Duke University Hospital, and that several people died at the scene.
Sheriff Tony Darden said all of those involved were adults and members of one family.
Darden also said the family had not previously asked the sheriff's office for help or filed a complaint.
Investigators were collecting evidence and interviewing people connected to the case, and authorities said there was no current threat to the public.
The identities of the dead and the suspected gunman had not been released, and the motive remained under investigation.