Patrons were seen being led out of the bar by deputies.
Authorities are still treating it as an "active scene".
'There were three or four and I hit the ground.
Hedge said he managed to run out the front door as the shooter made his way to the back of the restaurant.
Another witness said he saw a security guard being shot as well as a female cashier, before he also fled.
"The gunman was throwing smoke grenades all over the place", a different witness told KABC.
The gunman is described as having a beard and wearing a hat and glasses. People threw chairs out of the windows to try to get away. He had a big hand gun'. "He's taken many young lives".
Officers from the Ventura County Sheriff's Office and California Highway Patrol said about 30 shots were fired and several people were injured.
Police responded to the incident at around 11.30pm local time (7.30am GMT).
A police helicopter swirled overhead and officers surrounded the area with cars.
A SWAT team have been pictured surrounding the venue in their formations.
The gunman was still believed to be inside the bar an hour later, according to a police official.
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