People need to learn lifesaving skills in case they are caught up in a terror attack in the UK,
a team of senior military and civilian medics has said.
They say people need to know how to help each other because it could take some time before
it is deemed safe for paramedics to arrive on the scene.
Their app, called CitizenAID, offers step-by-step advice.
The idea is supported by counter-terrorism police.
Security services say a UK terror attack is highly likely.
'Run, hide, tell'
Although an individual's chance of being caught up in an incident is small,
Brig Tim Hodgetts and Prof Sir Keith Porter, co-developers of CitizenAID,
say it is a good idea for people to have a plan and the knowledge and skills to help each other.
Their app, pocket book and website suggest how best to deal with injuries in the immediate
aftermath of a mass shooting or bombing incident.
The system includes instructions on how to treat severe bleeding - one of the major causes of
death in these scenarios.
It guides people through packing, putting pressure on and elevating a wound,
and how to use a tourniquet safely, for example.
The programme also explains how to prioritise those who need treatment first and
what to tell the emergency services once they arrive.
CitizenAID is not a government initiative but its developers say it builds on
national advice from national counter-terrorism police to:
Run away in the event of an incident if you can
Hide if you can't run
Tell the emergency services.
CITIZENAIDThe system describes how to make a tourniquet out of a scarf to help stop bleeding
The CitizenAID system says people should follow these steps and then go one step further.
It suggests once people are safe, they should start treating casualties.
Ch Insp Richard Harding, head of the National Counter Terrorism Security Office,
told the BBC: "One of the challenges we have is that when a serious incident,
particularly a terrorist incident occurs, the first responders from a police perspective
to a terrorist incident will inevitably be trying to deal with the people causing the threat.
"They won't have time to deal with the people who are injured and that gap is vital to saving people's lives.
"So we are really interested in the concept of CitizenAID. It allows the public and people involved in very rare incidents like this to help themselves and help others and their loved ones survive the situation."
According to its founders, CitizenAID builds on lessons learnt on the battlefield.
Sir Keith Porter, professor of clinical traumatology at the Queen Elizabeth Hospital in Birmingham,
told the BBC: "I have treated hundreds of soldiers whose lives have been saved by simply the applications of tourniquets when they have been shot or blown up.
Teaching individual soldiers these skills has saved lives.
"And I think it is essential we train the public in those skills and that is exactly what CitizenAID does."
Brig Tim Hodgetts, medical director of the Defence Medical Services, told the BBC;
"We don't know when the next incident will be that will involve blasts or gunshots so we
need a critical mass of the general public to learn these first aid skills.
"They are the people who are always going to be at the scene.
They are the ones who are going to make a difference."
He added: "I think we are doing the opposite of scaring the public, we are empowering the public.
''By giving them a step-by-step system we take away the anxiety because the
decisions are already made and the right decisions in the right order can save lives."
The app is free to download and the pocketbook costs £1.99 to order.
Sue Killen, of St John Ambulance, added "First aid can be the difference between
life and death. Knowing basic first aid in a terror attack or in an everyday emergency at home or in the
community, will give you more confidence to deal with a crisis.
"First aid is easy to learn and our first aid techniques cover a wide range of injuries
that could occur in a terrorist incident including severe bleeding, crush injuries and shock.
"We encourage anyone who would like to learn first aid to go to our website to view our first aid videos,
download our app or attend a first aid course."