Manuel Vela was found dead in his jail cell at the Lerdo Max-Med Facility in California on Saturday afternoon, according to the local coroner's office.
The cause and manner of death has been unconfirmed by officials.
28-year-old Manuel Vela was accused of killing his girlfriend and unborn child in December 2016.
He confessed to murdering his girlfriend and unborn child after leading police on a pursuit. His girlfriend, Katrina Rivera, had gone missing days before.
Vela has been charged with two counts of first degree murder, recklessly evading a peace officer, and resisting an executive officer.