Christiansen was born in 1957 in Denmark and grew up in Solvang, California. He was a student and worked at a petrol station.
Between 1976 and 1979 he picked up young women hitchhiking or walking near bars and beaches in Santa Barbara and Los Angeles counties, shot them in the head with a .22 pistol, and in several cases interfered with the bodies afterwards. The victims were Jacqueline Rook, twenty-one; Mary Ann Sarris, nineteen; Patricia Laney, twenty-one; and Laura Sue Benjamin, twenty-one.
He was caught because a woman he shot in April 1979 survived and identified him.
He pleaded guilty and was sentenced to life imprisonment in June 1980. On March 30, 1981 he was stabbed to death at Folsom State Prison. The killer was never identified.
The case is one of a large group of southern California hitchhiking murders of the 1970s, a period in which hitchhiking was ordinary and the victims of these cases were routinely young women travelling alone by choice. That context is why several of these series took years to connect.