First that the participants behaved in what now seems strange:
• they would not go to a bank window if the teller was female
• they would check the bank balance, withdraw cash and then check the balance again, something that the banks now recognise was unusual
• they received money and then sent back whatever they had not used
• some of those involved had multiple accounts
• they purchased one-way tickets
• they paid for almost everything in cash – in a country where cash is not often used.
Secondly, they were very insular.
The Department of Homeland Security / FBI have issued a joint list of ways that might help identify a suicide bomber:
Indicative Behaviours of Suicide Bombers
• Clothing is out of sync with the weather
• Clothing is loose. Clothing gives impression that body is disproportionately larger than head or feet.
• Suspect may be carrying heavy luggage, bag, or wearing a backpack.
• Pale face from recent shaving of beard.
• Eyes appear to be focused and vigilant.
• No response to authoritative voice commands or direct salutation from a distance.
• Behaviour is consistent with no future, e.g. individual purchases a one-way ticket or is unconcerned about receipts for purchases, or receiving change.
• Suspect is walking with deliberation but not running.
Sherman Hospital in Illinois has added two more items to that list:
• Clenched fist that may be holding a detonator
• Wires hanging out of sleeves or clothing
But the danger is that we over-react and profiling becomes a serious problem.