Jade Douglas Harris, 30, pleaded guilty to a long list of charges, including three counts of murder, attempted murder, kidnapping and carjacking, the Los Angeles Times reported. Prosecutors have not yet said if they will seek the death penalty.
Harris allegedly killed two employees of United States Fire Protection Services in Downey and wounded the mother of the owner. He had gone to the business because of an ad on Craigslist for a 2010 Camaro.
The third victim, Susana Perez Ruelas, 34, had the Camaro parked at her home. Investigators say Harris forced her to drive him there and then killed her and shot and wounded her 13-year-old son.
The Times said records show Harris was paroled in July after doing time for robbery.
He is described as a member of the Rollins 40 Crips.