While it's not comfortable to acknowledge, terrorism is a real threat to our communities. During any type of terrorist attack your first priority should be to evacuate the area as quickly as possible. If evacuation is not an option, you need to arm yourself and prepare to fight.
During an attack of any kind (bioterrorism, active gunman, bombing) focus on evacuating yourself and those in need first. Keep your eyes open for any suspicious objects and stay away from them. Use your best judgment to determine if a bag left in the middle of the street was dropped by a fleeing individual or strategically placed by someone and if you feel it may be a threat, locate a first responder and let them know immediately.
If you have reason to believe that you have been exposed to a chemical or biological agent it is imperative that you take steps to avoid spreading it to other people.
If you are in a safe location, secure it by closing and locking all doors and windows (and blinds) and gather your evacuation kit in the event of an emergency evacuation order. Tune in to local news stations and listen for messages concerning what steps to take and any areas to avoid.