Tip:
Mass shootings have been more prevalent (or more visible) in the United States recently. Often the response is to ensure that we and our loved ones are carrying our defensive tools such as handguns, pepper spray, etc. Unfortunately, we have seen situations in which these tools would have done no good. So, what do we do to help?
Escape:
Based on you ability and opportunity, your best option might be to escape and help others escape immediate danger. This can be as simple as pointing out a readily available exit or holding a door for other potential victims.
Medical:
In any mass casualty event, you may be of more assistance in the aftermath than during the actual incident. If you can be of help to the responding medical personnel, it can certainly help them to be more efficient in their duties. This can be assisting in triage, moving ambulatory (walking)/non-emergent cases out of the way so first responders can immediately assess the most critical cases first. If you can respond with life saving knowledge and equipment, it is even better. Carrying a kit with you that is purpose driven to stop bleeding and restore breathing can save lives.
If you intend to help in this manner, you will need to have the knowledge necessary for triage and treatment. First aid courses are readily offered through the American Red Cross, and are important to know for everyday emergencies. Beyond this training, the Tactical Combat Casualty Care (TCCC) from the National Association of Emergency Medical Technicians (NAEMT) can help you with understanding triage and applications of easily carried medical equipment such as tourniquets. These courses and many like them are offered across the country.