Among the 12 victims are Ventura County Sheriff's Deputy Ron Helus, a 29-year veteran of the force who was the first to arrive on the scene, as well as actress Tamera Mowry-Housley's niece, 18-year-old Pepperdine student Alaina Housley.
Holden Harrah, who was at the bar, told CNN the gunman walked in and opened fire within seconds.
People run from the Route 91 Harvest country music festival after gun fire was heard, October 1, 2017 in Las Vegas. "And that's what's really blowing my mind, it's a really safe area". Other witnesses described people using bar stools to break windows and escape. Likewise, the shooter is dead, along with the first police officer to enter the bar ...
Ventura County Sheriff's Office Capt. Garo Kuredjian said late Wednesday that it was still "a very active scene".
Law enforcement agencies, firefighters and other first responders, along with several ambulances, additional units from the California Highway Patrol, Simi Valley and the Federal Bureau of Investigation, reached the spot soon after the shooting was reported. The Western-style bar hosts theme nights such as country, salsa and swing dancing.
Some of the classmates that teased Long were at the bar the night of the shooting.
Hundreds of people lined the streets to pay their respects as his body was taken by motorcade from the hospital to the coroner's office.
Authorities are investigating reports that the gunman used a smoke bomb but said they had not found anything to support this.
Sheriff Geoff Dean, who choked back tears while talking about Helus, said his friend had been talking to his wife when the shooting call came in.
There was no screaming, she said - just gunfire and stampeding crowds.
California already has some of the strictest gun laws in the country, but on Thursday, governor-elect Gavin Newsom promised he "will raise the bar" on gun control when he takes over in January. However, mental health specialists who were called in "talked to him, and cleared him".
"It was chaos, people jumping out of windows, hopping over gates and just trying to get out", he told the affiliate.
Media captionSurvivors of California shooting describe what they saw.
The incident was reported at the Borderline Bar and Grill in the town of Thousand Oaks, a quiet, upscale residential suburb of Los Angeles.