The gunman was dead inside the bar, Ventura County Sheriff's Sergeant Eric Buschow said, but he did not say how he died. The extent of the surviving victims' injuries wasn't immediately known.
A gunman entered a bar and dance hall in Thousand Oaks, California, late on Wednesday night and fired multiple shots, killing at least 11 patrons and a sheriff's deputy.
Shooting began at 11:20pm, where around 200 people were inside the country music venue.
"It was really, really, really shocking", she told KABC-TV as she stood with her father in the Borderline auto park.
Shortly before 1:30 a.m. Thursday, Capt. Garo Kuredjian of the Ventura County Sheriff's Office told reporters that the shooter was still "confined" inside the restaurant and that there was no longer an immediate threat to residents in the area.
There were roughly 200 people in the bar for a popular weekly "College Country" night, police said.
On Wednesday night, students gathered for college country night held between 9 p.m. and 2 a.m., according to the bar's website. "I could still hear gunshots after everyone left", the Times quoted the man as saying. Witnesses said he shot an unarmed security guard at the door and continued shooting anyone he could.
People were hiding the bar's restrooms and in its attic, Dean said. Authorities have not yet confirmed how the gunman died. "And I knew it was real".
A man who says he was in the bar tells ABC news reports that he saw a man shoot into the crowd.
Helus, a 29-year veteran of the department, was planning to retire next year, and Dean said he died "a hero".
"The reality is that these types of incidents can happen really at any place, at any time, even in communities that are considered extremely safe", he told CNN.
"It was chaos, people jumping out of windows, people hopping over gates to get out" Mr Steinwender told KABC. "From what I heard, the gunman started shooting at the front desk".
He claimed the neighborhood of West Hills, California, just 18 miles from Borderline Bar & Grill in Thousand Oaks, as his hometown, according to his Facebook profile, which has been refashioned into a "Remembering Ron Helus" page.