According to the Ventura Police Department, the officer, whose name was not released, was on duty and in police uniform at the time.
The coroner will determine the official cause of death.
The officer was discovered at 2:30 a.m. Officials said he had been missing for more than an hour. The computer was turned off in the police unit.
Police found the officer's car in front of a relative's home in east Ventura.
Officials said the officer was 27 years old and had been with the department for four years.
The Ventura County Sheriff's Department is taking the lead in the investigation as a courtesy.
No further details were available.