Study your surroundings. Find exits. Identify makeshift weapons. Americans are gleaning those tips and others as they pack classes on how to react to and survive a shooting.
Such training is already common at schools, colleges and businesses, but sessions for the general public are the next step in confronting fears of mass violence that have been around for years and, for many, came to a head after the 1999 Columbine High School shootings.
Police have offered the "awareness training" in Livonia, Michigan, and Douglasville, Georgia, while more than 600 people have attended classes taught by the Potter County Sheriff's Office in Amarillo, Texas, beginning about three years ago.
Public demand increased dramatically after the shooting in December that killed 14 in San Bernardino, California, said Lt. Scott Giles, a class instructor in Amarillo.
"This is really just something that was born out of necessity," Giles said. "Active shooter events just continue to happen."
Potter County is one of several sheriff's departments that provide training based on the CRASE curriculum: Civilian Response to Active Shooter Events. CRASE teaches an approach dubbed ADD: "Avoid" the situation by getting out, "Deny" by barricading inside a room, and as a last resort, "Defend" by fighting back.
A class offered by Westerville, a Columbus suburb, filled up so quickly that a second had to be scheduled for later this month. The city of about 38,000, with a per capita income well above the rest of Ohio, regularly tops lists of the country's best suburbs.
"We just feel the world has changed. There's evil out there," said retiree Tom Madine, 67, who attended the first Westerville class last month with his wife, Sue Madine, along with dozens of others.
People today understand that such threats are real and could happen in their own communities, said Police Chief Joe Morbitzer. Officers teach a "Run, Hide, Fight" curriculum similar to ADD.
"Part of the issue is that people don't know how to avoid becoming victims," Morbitzer said. "In today's society that's bad, that you've got to practice victim avoidance, but you have to."
At the Jan. 28 Westerville class, officers Dan Pignatelli and John Jeffries emphasized "situational awareness."
They mixed practical tips — for instance, the best exit in an emergency is not always the way you came in, and if you're hiding, always turn the lights off — with case studies from the 1999 Columbine shooting, the 2007 Virginia Tech killings and others.
As a last resort, a weapon could be as near as the closest chair, pair of scissors or blunt object, they said.
"You've got to have a game plan," Jeffries, a 31-year police veteran, told the audience. His comment was part of a bigger point both instructors drove home throughout the two-hour class: that people must overcome inaction when something bad happens.
Instructors in Ohio and elsewhere don't take a position on whether people legally allowed to carry a gun should intervene to stop an attacker. But they worry about what happens once police arrive.
"When a civilian, let alone a trained officer, opens up firing in an active shooter situation, there is a good chance that civilian may be mistaken for the shooter," said Philip Schaenman, a security expert who has studied some of the country's worst shootings, including Virginia Tech.
Denise Bunsey attended the January class in Westerville with her parents. Afterward, the 36-year-old guidance counselor said the most important lesson was that people have options even in worst-case scenarios.
"Despite what's going on, you really have to have the mindset of, 'I will survive this and I will do anything I can to survive this,'" Bunsey said. "I never thought about it in that way."