The incident happened November 11 around 10:40 p.m.
Police responded to the intersection of Center and Cumberland Streets in Bangor and found Jason Moody, 40, unconscious in the street after an apparent fight.
Moody was taken to the hospital, but was pronounced dead Tuesday as a result of his injuries.
According to the Chief Medical Examiner, Moody's death is a homicide.
Bangor Police are now looking for Donald Galleck, 29, in relation to the incident.
He is believed to be in the Bangor or Old Town area.
Anyone with information about the incident should contact the Bangor Police Department.