Giovanni Gallardo, 18, convicted of murdering girlfriend's parents to fund Halloween party

(CBS/AP) LOS ANGELES - Prosecutors say 18-year-old Giovanni Gallardo has been convicted of murdering his girlfriend's mother and stepfather and now faces a possible life sentence.

City News Service reports a Compton, Calif. Superior Court jury found Gallardo guilty of two counts of murder after about 90 minutes of deliberations on Wednesday.

Gallardo was 16 at the time Gloria Villalta and Jose Lara were killed in 2011.

Cynthia Alvarez, Gallardo's girlfriend who was 15 at the time, was convicted by a separate jury in the murders after testifying she and Gallardo stole the victims' jewelry and truck parts to fund a Halloween party.

The two went to a party supply store with her dead mother's body in the back of the car.

The decomposing bodies were found buried in shallow graves days after their killings.