Mother Jones reports that Amendment II, a Salt Lake City-based company that manufactures lightweight body armor for law enforcement and military use, has seen its sales of bullet-proof backpacks go through the roof. "I can't go into exact sales numbers, but basically we tripled our sales volume of backpacks that we typically do in a month—in one week," company president Derek Williams told Mother Jones.

The company website explains how to use the bullet-proof bags in an emergency: "Hold bag between yourself and the shooter using the straps as handles. Use as a shield to provide cover for upper torso and head whenever possible. While taking shelter use bag to protect yourself in the direction of the threat. While running away, hold bag high on your back or in the direction of the threat to protect your head and upper torso (vital organs)."

It's not just the shooting that has people frightened. "A lot of people buy body armor for the breakdown of society and government," Williams told Mother Jones.