I-Team Reporter Dan Noyes has some advice from the experts.
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RESOURCE: Florida State's active shooter training video
Just this past weekend, Dan's teenage son was heading to an all-age concert in Berkeley. And he felt he had to remind him to check for the fire exits -- have an escape plan if a fight breaks out, a fire ... or a shooting. That's our world now.
"We thought it was a joke," a witness said of the mass shooting in Thousand Oaks. "We didn't take it seriously at first, it's like you kind of freeze because it sounded like firecrackers."
College night at the Borderline Bar and Grill, shattered by gunfire.
RESOURCE: US Department of Homeland Security video on how to prepare for active shooters
A mass shooting is the type of event for which Oakland Unified Police Chief Jeff Godown trains district teachers and supervisors. ABC7 was there for the session from February of this year.
"Your viewers are going to roll their eyes and say, 'Chief, are you saying every time I go outside my door, I've gotta be paranoid of this?' I'm not saying that, but you need a plan," says Chief Godown.
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MORE: Video captures Thousand Oaks gunman shooting inside bar
Video captures Thousand Oaks gunman shooting inside bar
The chief says, no matter where you go, know your exits and be prepared to run, hide or -- as a last resort -- fight if something terrible happens. "It is a sad commentary on the world that you have to go up to your 3-year-old today and say, 'Listen, if someone tries to kill you, this is what I want you to do,' and that's the world that we live in."
You've heard the stories of heroism coming out of the Thousand Oaks shooting, how a few people saved many lives.
"So then our friends got the bar stools and they started slamming them against the windows so we could get out," a witness said. "That's how we were able to get out, they broke the window."
MORE: How to help victims of Thousand Oaks mass shooting
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The experts say we should prepare ourselves mentally, to react to such emergencies, by doing the research -- much of it available online.
"When startled by a gunshot, it's a natural human reaction to freeze," says a training video narrator.
But, freezing leaves you vulnerable, according to this video published by the US Department of Homeland Security in August. It says most active shooter events last between 90 seconds and three minutes. So, actions you take may make just as big of a difference as those of law enforcement.
"If you are confronted by the active shooter, you have to assume that your actions are all that stand between yourself, your colleagues and grave harm," says the DHS video. "Fight for your life."
Chief Godown tells us he is now working on active shooter training for students, figuring out how to make age-appropriate videos that won't scare the younger kids too much. This is now a conversation we can't avoid.
Visit this page for more stories and videos related to the Thousand Oaks mass shooting.