Revelers will flock en masse to ring in the new year at public gatherings across the country, but partygoers should be prepared for worst-case scenarios, one expert warns.

"It seems like these days, every other week there is another case where a person with a firearm has decided to attack innocent people," said Joey Walker, a retired police lieutenant and current self-defense instructor.

"There are many reasons why these mass shootings occur from people who are acting out of anger, to mental illness and everything in between. … When such a person decides to go on such a killing spree, they are not only homicidal but suicidal as well."

In an interview with Fox News Digital, Walker outlined what steps people can take when faced with the terror of an active-shooter situation.

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Tmes Square in New York City during the 2023 New Year's celebration

Revelers celebrate New Year’s Eve in Times Square, New York City, on Jan. 1, 2023. (Alexi Rosenfeld/ Getty Images)

Walker, a self-defense expert who has written books and trained civilians how to be safe in a variety of situations, said the phrase "Run, Hide, Fight" during an active-shooter situation "needs to be revamped to Run, Hide, Ambush."

He broke down each verb with instructions and strategies.

Run 

When gunshots ring out, Walker said there are two key determinations to make: Are you close or far from the gunman and what direction are the shots being fired?

People trying to escape the bullets often try to call 911 while fleeing, which Walker said is a mistake.

"Your first priority, if possible, is to escape from the kill zone," he said. "Once you are in a safer place, then call 911 to report the shooter."

Robert Card

Robert Card is shown in this video image during his shooting rampage in Lewiston, Maine, on Oct. 25, 2023. Card fatally shot 18 people and injured 13 others. (Lewiston, Maine, Police Department)

Walker advises to "drop low to the ground and attempt to get behind some object that might stop bullets from striking you."

"If you need to escape from the immediate area, you may need to move from one position of cover to another until you have escaped from the entire area," he said.

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Hide

Choosing where to hide is essential.

Walker said a room or building where the shooter hasn't entered and has a door that can close and lock is preferable. Then barricade the door, shut off the lights and move away from the door to a corner where bullets aren't likely to hit you.

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But you need a backup plan, according to the self-defense expert.

"If you have elected to hide from the shooter, chose a place where, if the shooter were to breach your concealed location, you will be capable of your last line of defense: fighting for your life," Walker said.

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"Locate and be prepared to use improvised defensive weapons, such as sharp or blunt items, should the shooter breach the room. Listen for the shooter as the person moves through the area. Should you hear the shooter approach your location, this is the time for you to get ready, just in case the shooter attempts to enter."

Ambush

This is the last resort.

"From teaching active-shooter defense, I advocate not throwing things or charging the shooter, all of which are dangerous, and the shooter may elect to shoot that person next," Walker said.

"Instead, be prepared for the shooter from your concealed hiding place. Place yourself in such a position where you can use an improvised defensive weapon to launch your counterattack against the shooter."

Raul Mendez

Raul Mendez survived a mass shooting in which he was shot in the head and even managed to thwart the shooter. (NRA)

Using a sharp object, strike the shooter's eyes or throat, Walker said. If your defensive weapon is a blunt item, hit the shooter in the head or the face.

Being this close to a gunman is only a last-stand effort, especially if you're not trained in self-defense, he said.

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Walker teaches his students how to multitask in a hand-to-hand combat situation where "you might need to move the barrel of the firearm away from you while at the same time initiate a quick set of strikes to disable the shooter.

"Once you have disarmed and disabled the shooter, if the opportunity exists, escape from the area," Walker said. "If there is or maybe a second shooter and their location is unknown, remain in your concealed location and be prepared to defend yourself should the need arise."