Brian Hynes appeared on CNN, where he said he's owned the bar for a decade but had been a longtime customer for years before that.
Hynes said he got a call about the shooting and arrived at the scene as it was still happening.
"So I just saw, obviously, some havoc, and police were already there. There was the two officers that had gotten there early, and there was still some shooting going on. I heard a lot of the explosions from the smoke bombs. People were trying to just...come to grips with what was going on," he said.
Hynes said if possible after the healing process, he would one day like to reopen the Borderline Bar & Grill.
Twelve people, including college students and a Ventura County Sheriff's Department sergeant, were killed Nov. 7 when a gunman opened fire on patrons at the country-themed bar.
MORE: Remembering the victims of the Thousand Oaks mass shooting
Authorities have not publicly shared what motive they think might have led suspected gunman Ian David Long to go on the killing spree before shooting himself that night.
The Borderline Bar and Grill remained roped off with crime tape Monday. People stopped by a nearby memorial for victims, which includes 12 large white crosses with every victim's name on them.