How would you respond if someone opened fire at work? How should you respond? And what can you do to prevent such a thing from happening in the first place?

Local law enforcement officers tackled those questions Wednesday afternoon at a lunch presentation hosted by the South Coast Metro Alliance's Business-Police Partnership.

The event brought together various public safety agencies, area business leaders and school officials. About 64 people attended the lunch at the DoubleTree Hotel in Santa Ana. The alliance represents businesses near South Coast Plaza, where Costa Mesa and Santa Ana share a border.

In the wake of recent high-profile active shooter situations, like the Aurora, Colo., movie theater shooting, speakers said it's more important than ever to have an emergency plan in place and to understand how best to help first responders if an incident does take place.

Above all, speakers emphasized awareness about active-shooting incidents, which are loosely defined instances of killing or attempted killing in a confined, populated space, usually using firearms.

Taking the attitude that "it couldn't happen here," speakers said, could be a dangerous mistake.

"You have to understand this isn't just your workplace anymore," said Craig Farrow, assistant director of South Coast Plaza Security, who helped organize the event. "This is anywhere you may go."

Shawn Dyball, an investigator with the Orange County Intelligence Assessment Center, discussed methods for recognizing possible danger before workplace or school shooters reach a violent "flashpoint."

"The key here is that it's preplanned. Active shooters don't just snap," she said. "Somebody that conducts the shooting in the workplace, with very, very few exceptions, they don't just happen to have a gun handy, get pissed off and decide to go shoot somebody that they don't get along with."

Instead, most shooters have become hostile over a longer period of time, sometimes as a result of work-related stresses, or issues in their home lives, she said.

Members of the audience gasped when Dyball said many shooters involved in past killings practiced using weapons in the time leading up to the events, as in the case of the 2007 Virginia Tech massacre.

Having a safe, anonymous reporting system for employees who are concerned peers may become violent is key, she said, as confronting a troubled employee directly can be counterproductive. She also stressed that employees or students in a workplace should be very familiar with emergency exit plans.

Dyball added that all employees should know to tell 911 dispatchers what city they're in, because 911 calls from cell phones go directly to California Highway Patrol — not the nearest law enforcement agency.

Santa Ana Police Department SWAT commander Doug McGeachy said it's a common misconception that SWAT teams are first responders to active shooting calls.

"By and large, an active shooter incident is not a SWAT incident," he said. "That an active shooter [requires] a SWAT response was conventional wisdom up to Columbine. We were very, very wrong and we had to change the way we thought about that in law enforcement."

He said police officers will most likely be first responders to calls of an active shooter, adding that their first priority if violence is ongoing will be taking out the shooter, so they may not respond to cries for help.

The afternoon's presentation ended with a screening of a short video produced by a Department of Homeland Security grant initiative called Ready Houston, which gives more specific instructions in the event of a workplace shooting. The video encouraged a strategy it called "Run. Hide. Fight."

Though he said the school reworked its emergency lockdown plans over the summer, Costa Mesa High School Assistant Principal David Peterson said he plans to show the video to teachers as an additional part of their training.

Peterson said lockdown situations have always been on his radar as an educator, but "Columbine raised it to a whole new level."

Still, he said, violence is "nothing anyone sort of broods about all the time."

jill.cowan@latimes.com

Twitter: @jillcowan