"You have to expect it. It is the new norm."
"This incident at the Walmart in El Paso should really wake a lot of people. It can happen anywhere," Shaffer said.
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Shaffer spent 20 years with the FBI and now teaches companies how to prepare for active shooters. He said it starts with being aware of your surroundings and following your gut.
"[Be aware] who's around you, what's around you, where are the exits?" Shaffer said. "Just be casually aware and if you hear something that sounds like gunfire -- think gunfire."
Shaffer said there are lessons we can learn from each tragedy. Running away from gunfire is the most important, and he stressed that hiding can make you a target.
He preaches the acronym ADD - avoid, deny and defend.
"First and foremost thing you do when you hear gunfire is move," Shaffer said. "You avoid the shooter if you can. If you can't run, you hard-point. You go into a room and deny him access. Once you do that, now look for ways to defend yourself."
Shaffer said it's important families, schools and companies practice active shooter drills just like they would fire drills and tornado drills.
"We need to practice with our kids and our family members what to do during an active shooter and that's avoid, deny and defend," Shaffer said. "If we can get that mantra and that programmed into our kids, I think we'll save more lives."