Los Angeles fire officials are dramatically changing how rescuers respond to mass shootings after a gunman with a high-powered rifle mortally wounded a federal security officer in a shooting rampage last month at LAX.

The new goal is to have Los Angeles Fire Department paramedics and firefighters, protected by armed law enforcement teams, rapidly enter potentially dangerous areas during active shooting incidents to treat victims and get them en route to hospital trauma centers.

"The LAX incident really was a paradigm shift for us," said Fire Department Medical Director Marc Eckstein, an emergency room physician and proponent of the more aggressive approach to rendering medical aid. "There are people whose lives may depend on us getting them out of there quickly."

Tactical changes had been under consideration but were accelerated and disseminated through the ranks after the Nov. 1 shooting of Gerardo I. Hernandez, the first Transportation Security Administration officer killed in the line of duty.

That morning when rescuers arrived at Los Angeles International Airport, they set up a safe distance away and waited 15 minutes before they were told that Hernandez was lying by an escalator near the entrance of Terminal 3, according to interviews and dispatch logs obtained by The Times.

Police moved Hernandez to paramedics using a wheelchair, and he was taken to a Carson-area trauma hospital, where he was declared dead.

A coroner's autopsy report found 12 bullets had ripped through the 39-year-old officer's heart and other organs, and Los Angeles police Chief Charlie Beck has said no rescue effort could have saved him.

Hernandez's death added new urgency to overhauling the Fire Department's response to shooting rampages in which gunmen haven't been apprehended.

With the changes, the department joins a growing number of fire agencies that are borrowing battlefield tactics of military medics to improve the odds of saving victims.

More than 250 people have died nationwide in mass shootings since 1999, federal officials note, including attacks last year on moviegoers at a Colorado theater and students at Sandy Hook Elementary School in Newtown, Conn. The new imperative, experts say, is to reach those with life-threatening wounds quickly, stem their bleeding and get them to trauma centers as fast as possible.

"They need a surgeon," said Battalion Chief Jeff Adams of the Orange County Fire Authority, which has rewritten procedures and retrained hundreds of rescuers in revised emergency response tactics being championed by the Obama administration.

Recommendations issued by the Federal Emergency Management Agency in September call for fire department medics, working with police, to enter "warm zones" — areas near active shooters where a threat might exist — before the attackers have been fully contained.

Frontline rescuers in communities of every size need to be prepared, said U.S. Fire Administrator Ernest Mitchell Jr. "This can happen anywhere, any time. We don't want to wait until after the fact and say what we would have done."

Traditionally at shooting scenes, fire department rescuers have been held back in safe "cold" zones, awaiting orders to go to victims from law enforcement officers clearing "hot" areas where gunmen are active. Hot and warm zones are dynamic, experts say, and can change depending on the movements of the shooter.

The long-accepted tactics began to be scrutinized more closely in recent years with a rash of shooting incidents, starting with the 1999 Columbine school massacre in Colorado, when 13 people were slain by two gunmen who fired more than 100 rounds. Medical crews there were waiting nearby as a teacher bled to death.

An October 2011 attack on a Seal Beach hair salon by a gunman, who killed eight people, prompted Orange County to move to the forefront of large California jurisdictions embracing the new approach to mass shootings.

Nearly 1,000 Orange County Fire Authority personnel have been trained to don ballistic vests and enter warm zones under the protection of law enforcement officers, officials say. In addition, about 500 patrol deputies from the Orange County Sheriff's Department have been trained to treat gunshot wounds and issued lightweight first-aid kits.

"It's super-simple stuff. You're slowing down or stopping the flow of blood," said sheriff's Sgt. Christian Hays, who has been conducting the deputy training. "The first-responder community is long overdue for this."

In Los Angeles County, fire and police agencies say they need to revamp their responses but are trying to determine the best way to work together, said Dr. William Koenig, medical director for the countywide agency that oversees emergency medical care.

A training bulletin issued by interim L.A. Fire Department Chief James G. Featherstone provides new direction on dealing with law enforcement to set up warm zones and deploying "rescue task forces" to search for victims.