Gargiulo, 43, was convicted in August of two counts of first-degree murder, one count of intentional, intentional and intentional attempted and attempted escape, according to a news release from the DS's office.
Jurors, composed of six men and six women, deliberate for "several hours" before reaching the death sentence, the release said.
Second murder victim, Mario Bruno, neighbor of Gargiulo, was killed and maimed in December01010. 2008 Gargiullo is attacked and stabbed to death by Michelle Murphy. He was accidentally interrupted by the attack, which allowed investigators to link DNA to other killings, the KABC reported.
Gargiulo's sentencing is scheduled for February 28, the DA's office reported. The judge will have the final decision.
He was also charged with murder in 1993 in the Chicago area, the DA's office said. Prosecutors allege that the victim, Tricia Pacacho, was Gargiulo's first. At that time, he was 17.
CNN contacted Gargiulo's lawyer, but has not yet received a response.