A man walked into a police station to reveal he had killed four of his family members and had the body of one relative in his car boot.
The man, whose name has not been released, had driven more than 200 miles from his apartment in California to report the deaths at a small-town police station in Mount Shasta.
Sergeant Robert Gibson, who was working at the station, said police did not initially believe the man, who was calm and "matter of fact", until he handed them keys to a red Mazda.
"He just came in and told our dispatcher that I want to confess to a murder, and then just gave it up," he told the New York Times.
"I have never had someone come in with a body and turn themselves in here.
"This was unusual for us."
Officers examined the body in the car before sending Roseville Police Department to search the man's home address.
Three additional victims were found dead at the scene.
Police have launched an investigation and are obtaining search warrants in connection with the deaths.
A Mount Shasta Police department spokesman said: "The sole suspect involved in this incident is in custody and we do not believe there is any ongoing threat to the community."
