Updated

A Marine has been arrested in San Diego for allegedly murdering his infant son.

San Diego police say 22-year-old Michael Bixby was arrested Tuesday when he came to police headquarters for follow-up questioning about the death of 4-month-old Andru.

Lt. Ernie Herbert says Bixby was caring for the infant last Wednesday when the boy stopped breathing. Police say Bixby started CPR and the baby was taken to a hospital where he died the next day.

The medical examiner's office later said an autopsy showed the infant died from blunt force head trauma.

Bixby is based at San Diego's Miramar Marine Corps Air Station.