The truth is that the best thing you can do at your place of business, your child's school, or your place of worship is to have a PLAN IN PLACE in the event that a terrorist incident occurs. Think about what would happen if an armed gunman or a suicide bomber entered your place of work - someone may sound an alarm and everyone would follow the fire escape plan. Good idea? Is it a good idea to have everyone congregate in the lobby or right outside the building, as is usual for fire escape plans? Think about it for just a moment - there's a guy with a bomb whose overriding goal is to cause mass casualty, and your fire escape plan gives him exactly what he wants, huge numbers of people all congregated in one place. Just to be clear - this is a terrible plan. A fire evacuation plan is great for fire but not great for active shooters or bomb threats.
Your place of business needs to have a plan in place for what to do in a situation like this. This is called an Emergency Action Plan, and it goes far above and beyond a simple fire evacuation plan. A proper Emergency Action Plan will have different plans for different scenarios - fire, cataclysmic weather, active shooter, or maybe even an irate parent or client.
Don't wait until it's too late. Think about having a risk assessment done for your place of business. Ask your child's school administration if they've ever done a risk assessment and if they have an Emergency Action Plan (NOT just a fire evacuation plan). Ask the security guards at the front desk of your multi-story office building if there is an Emergency Action Plan for the building. Ask your boss if there is one for your company. Don't be afraid to speak up at your place of business or your child's school and ask about a risk assessment and an Emergency Action Plan.