Shots are fired; victims are down. Police and paramedics flood the scene. But the gunman is still on the loose inside the building.
When should the paramedics go in to help wounded victims?
In the past, they have waited outside, sometimes for hours, even as patients lay injured and in need of medical help inside a school or workplace. Because paramedics weren't trained or equipped for such dangerous situations, they waited until police apprehended or killed the assailant and searched the building to ensure it was safe.
But under a new policy being put into place across Orange County this summer, paramedics will be able to go in and try to rescue or treat victims even if the shooter remains at large.
"It can be eight hours until it's all clear, and in that time we have savable people who are dying while we're on scene. And that's unacceptable," said Jeff Adams, an Orange County Fire Authority battalion chief who helped draw up the new policy for such "active shooter" scenarios.
Under the new policy, approved by all 11 fire departments in the county, paramedics or firefighters would wear ballistic vests and helmets and enter the building with a police escort as a "rescue group."
The tactics, and the potential dangers, are similar to those on battlefields.
"It's like a military operation: You've got people in there securing the perimeter while you're treating the patients," said Chip Duncan, acting assistant chief for the Newport Beach Fire Department. "It's a whole different mindset: We're going in."
Orange County's shift in tactics is part of a national reassessment of how police and fire departments respond to mass shootings.
A national debate began after the 1999 shootings at Columbine High School in Colorado, where 13 people were killed. Paramedics and police waited for hours to enter the school, possibly costing the life of at least one person, teacher Dave Sanders, who lay bleeding in a science room for hours. The two shooters had been dead for hours while they waited, but no one knew that.
In Orange County, fire departments had talked about the need for a new "active shooter" plan for close to a decade, Adams said.
But progress lagged until eight people were killed at a Seal Beach salon in 2011. Then came the shootings last year at a movie theater in Aurora, Colo., and an elementary school in Newtown, Conn.
Tom Schultz, a Fullerton Fire Department deputy chief who chaired the committee that wrote the new policy, said the Aurora shooting brought the issue to the front burner again.
Though Orange County has had active shooter drills and training over the years, this marks the first widespread coordinated shift in tactics.
"It's been a long time coming," Adams said.
'This is our job'
Deciding to send paramedics into a building where a shooter could be roaming marks a major shift in thinking, Adams said.
But, after all, firefighters run into burning buildings.
"We have to realize as the fire department that, hey, this is our job," said county Fire Authority Capt. Mike Morganstern, who helped write the new plan. "I'm sorry, but we get paid to risk our lives. That's what you signed up for."
Todd Baldridge, one of the directors of the union representing 1,000 Orange County firefighters, said he and his members support the plan because it makes the public safer and takes the safety of firefighters seriously.
Under the plan, medics will go in only if police think it's safe enough. Officers will aim to clear the area immediately around patients while paramedics get in and get out.
Officials couldn't say whether such a policy could have saved any of the Seal Beach shooting victims. But it's clear it could save lives in the future.
The International Association of Fire Fighters, with more than 300,000 members, supports a similar concept of "rescue task forces" that include paramedics.
Firefighters have long faced danger beyond fires. More than 20 years ago, many from Orange County faced gunfire when they went to Los Angeles to help during the riots.
That led many departments here, including Newport Beach's, to buy bullet-resistant vests and store them on fire engines.
As he helped draft the new plan, Morganstern looked at those already used by SWAT team medics. In some jurisdictions, armed and specially trained "tactical paramedics" go in with police on high-risk raids so they can give immediate care if an officer is shot.
Under the new Orange County plan, medics will not be armed. And instead of training a few people as tactical paramedics, fire and police departments will train everyone in the new active shooter protocols.
The county's fire operations chiefs appointed a subcommittee to write the new active shooter policy. Over several years, its membership fluctuated from about seven to 12.
They finished the plan late last year and, after reviews and approvals by fire and police chiefs and unions, held "train the trainer" sessions in May and June.
The 60 people who went to those sessions will now begin training thousands of rank-and-file firefighters, police officers and sheriff's deputies. That should be done by the end of summer, Morganstern said, and there's a large live-action drill planned for November.
After that, it's a matter of preparing for a day everyone hopes never comes in Orange County. Schultz said firefighters here will be better prepared for that day than almost anyone else in the country.
"By us getting in there quicker and rendering aid, we can save a lot of lives," he said. "There's no two ways about it."