Events such as the terrorist attack at Westminster recently are, thankfully, rare.  However, being informed what to do, and not to do, in such events can help protect people from harm. 

There is a delicate balance to achieve between helping people have useful knowledge and not causing unnecessary alarm and fear by sharing  that information. 

The general consensus from the corporate security community is to share Government and/or publically available information.

The UK Govt have developed the 'Run, Hide, Tell' campaign http://www.npcc.police.uk/NPCCBusinessAreas/WeaponAttacksStaySafe.aspx that covers the basics of what to do if you find yourself caught up in a major incident. 

CitizenAID provides even more useful information, including first aid information, and is available in a useful App. 

http://citizenaid.org/

citizenAID™ is the initiative of four deeply experienced UK civilian and military clinicians working in collaboration with industry to improve public resilience.

When there is a shooting, stabbing or bomb explosion the initial priority will be public safety. This can delay the time before the emergency services are able to reach the injured. citizenAID™ enables the general public to be effective in these situations before the emergency services are available to provide professional medical support.

citizenAID™ is a simple, logical system of immediate actions. It is designed to guide the public to react safely, to pass effective messages to the emergency services, to prioritise the injured and to give life-saving first aid.