At least 12 people were killed.
Long reportedly shot a bouncer or security guard outside and forced his way into the bar, witnesses said.
"It was just shots and smoke... he was shooting everything - from the speakers to anything - so all we really saw was smoke", Summer Helmuth, who is in the military and visits the bar about once a week, told local outlets at the scene.
Holden Harrah told CNN the gunman opened fire within seconds.
'All I wanted to do was get as many people out as possible, ' he said while wearing a bloodstained t-shirt.
Helus was immediately hit with multiple gunshots, Dean said.
"It's a horrific scene in there", Dean said at a news conference early Thursday in the parking lot of the Borderline Bar & Grill. The highway patrolman cleared the perimeter and pulled Helus out. Long was found dead at the scene, having apparently shot himself.
"I think everyone was in so much shock that it was sheer panic", she said. Long used an extended magazine for the weapon, Dean said.
"We have not found any type of assault rifle inside the location", he said.
Kelly has a large tattoo on his left arm memorializing the Las Vegas shooting, which killed 58 people.
Helus was a 29-year veteran of the force with a wife and grown son and planned to retire in the coming year, said the sheriff, who choked back tears several times as he talked about a man who was also his longtime friend.
Alaina Housley, a student at Pepperdine University, was reported missing following the shooting by her suitemate.
"I don't know how to console or what to say to the other people who are going to go through the same thing as I am".
Authorities have not released numerous victims' names but among those who have been confirmed are three men and one woman.
President Donald Trump was briefed on the shooting and praised law enforcement officers for their response.
"This is a very close-knit community", Kuredjian said, adding that Thousand Oaks - north and west of Los Angeles - is a "pro-law-enforcement community" as well.
Wennerstrom told CBS News he was a weekly regular at the Borderline Bar & Grill, and the other customers were like "family".
The Borderline bar is a popular spot for university students, and on Wednesday night was hosting College Country Night. More than 100 people were inside the venue at the time of the attack.
I have been fully briefed on the bad shooting in California.
Nicholas Champion was among those who survived both shootings and spoke about his experience to CBS News.