The sheriff in the city of Thousand Oaks named the shooter as 28-year-old Ian David Long, and confirmed he had been found dead inside the bar.
One of Sheriff Geoff Dean's deputies, Sgt Ron Helus, was among those killed, after he responded to emergency calls around 11.20pm local time on Wednesday.
Also among the dead was 22-year-old Cody Coffman, whose father Jason confirmed his son had been killed in the attack.
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