Helus, who lived in neighboring Moorpark with his wife and son, died at about 2 a.m.at a hospital.
The gunman, who is believed to be among the dead, burst into the bar around 11:20 p.m., cloaked in all black as he threw smoke bombs and began shooting at targets as young as 18 authorities and witnesses said. It is yet to be determined if he shot himself or was shot by other officers, according to Ventura County Sheriff Geoff Dean.
Dean said Long was known to officers through a minor traffic collision and was a victim of a battery incident at a different bar.
Police said Long appeared to have shot randomly into the crowd at the Borderline Bar and Grill in Thousand Oaks, about 50km west of Los Angeles. The bar was hosting a college country music night and was packed with students and other patrons.
"Ron was a hardworking, dedicated sheriff sergeant", Dean said while holding back tears.
"It was chaos, people jumping out of windows, hopping over gates and just trying to get out", he said. It also came less than two weeks after a gunman massacred 11 people at a synagogue in Pittsburgh.More news: Diablo Immortal: Fans Loudly Deny Blizzard's New Mobile Venture!
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Deputies were called to Long's house in response to a disturbance in April, 2018 and "felt he might be suffering from PTSD", he said. Add Thousand Oaks Shooting as an interest to stay up to date on the latest Thousand Oaks Shooting news, video, and analysis from ABC News.
When the shooting was over, 13 were dead, including the shooter who was found by responding officers.
Gina Silva and Gigi Graciette reported from Thousand Oaks, Calif. Lisa Fernandez wrote from Oakland, Calif.
The police captain also did not know whether the gunman had been "neutralised" or not calling the situation "fluid".
The suspect, who was armed with a.45-caliber handgun, was found deceased at the Borderline Bar and Grill, the scene of the shooting in the city of Thousand Oaks northwest of downtown Los Angeles. Dean says Helus was his longtime friend and gym partner and planned to retire soon after 29 years with the force.
They survived the deadliest mass shooting in recent USA history just over one year ago. Jason Coffman told reporters Thursday that his oldest son, Cody Coffman, was killed. A California Highway Patrol officer who was entering with him retreated, secured the perimeter, then pulled Helus out of the line of fire.
He said both they both managed to escape. "I don't know if she is alive", he said.