A 15-year-old has been charged as an adult after admitting strangling his foster parents and hiding their bodies in the family car.

California prosecutors claim that Moses Kamin, a black belt in karate, killed the pair after an argument about the amount of time he was spending at the Occupy Oakland camp.

The bodies of Robert Kamin, 55, and Susan Poff, 50, were found under blankets in the vehicle outside the family home.

Scorch marks were found on the car, suggesting that the suspect had attempted to set the petrol tanks on fire. He was arrested and confessed to strangling the couple.

The San Francisco Chronicle reported that he had been adopted within the last 10 years and friends claimed that he frequently clashed with his foster parents.

They argued about the amount of time he was spending at the Occupy Oakland camp, which he ran away to join in November. He was recently suspended from school.

Police claim that the boy strangled Poff after an argument before hiding her in a room and waiting for her husband before killing him.

Co-workers of the dead man alerted the authorities when he did not show up for work the following day.

Joshua Bamberger, a colleague of Poff, told the Oakland Tribune: " I have never met anyone who lived with as little ambivalence about making the world a better place. She was one of the most loving, heartfelt, solid and wise persons who ever cared for people living in poverty".

Robert Kamin worked as a psychologist for the San Francisco prison service and Poff treated homeless patients at a clinic.