"Sergeant Helus served with the Ventura County Sheriff's Office for 29 years and is survived by his wife and son".
Sheriff's Capt. Garo Kuredjian said deputies could hear gunfire when they arrived. "My heart goes out to his family - I can't imagine what they're going through right now".
"I saw the shots go off, although I didn't really see the guy", she said.
The shooter reportedly stormed into the venue wearing a black trench coat, armed with smoke grenades and a firearm with a high-capacity magazine.
Prior to getting the call to respond to the shooting, Helus was speaking with his wife on the phone, said Ventura County Sheriff Geoff Dean. On Oct. 27, a gunman killed 11 people at a synagogue in Pittsburgh. The shooter, a former US Marine who was believed to be suffering from post-traumatic stress disorder, was killed.
"There were people hiding in restrooms, people hiding in attics", Dean said. The venue, which describes itself as the county's largest country dance hall and live music venue, was hosting a "College Country Night".
"Hey, I gotta go handle a call".
He said that there are at least "six victims including one deputy" who are still inside the bar.
California Lutheran University confirmed that Mr Meek, a recent graduate of the university, was "one of the precious lives cut short in this tragedy".
Two passersby who said they had friends who visited the bar frequently told NBC Los Angeles that they spoke to one man who had managed to escape the bar.
"Ron was a hardworking dedicated sheriff's sergeant", said Dean, trying to hold back tears. People dropped to the floor and hid behind bar stools in stunned silence.
UPDATE 6:30 a.m.
Thirteen people were killed in a shooting at the Borderline Bar & Grill in Thousand Oaks, including the shooter and Helus. He was set to retire next year, CNN reported.
"I've learned it doesn't matter what community you're in", Dean told reporters when asked if he was surprised this happened in Thousand Oaks.
Kuredjian said at around 0915 GMT (5pm Singapore time) that the shooter was still confined inside the premises, adding that he did not know if he had been subdued or shot.
ORIGINAL 5:44 a.m.
Authorities said he was about a year from retirement.
A college country music night was under way when the suspect, apparently dressed in black, entered the bar and opened fire.
Ventura County Sheriff's Office Sgt. Eric Buchow told the station there were "multiple fatalities" and the gunman was dead inside.