After each UK and I expect in the USA too questions are asked of law enforcement (and intelligence agencies) whether they knew of the attacker's intentions beforehand.

It now appears that the suspect in the recent knife attack @ Leytonstone Tube Station, in East London, may have been signalled on mental health grounds three weeks before to the police beforehand by his own family and the Met say without mention of him being radicalised:http://www.telegraph.co.uk/news/ukne...-in-court.html

A recent Soufan Group newsletter asks how can a CT network adjust fully to a silent two person attack i.e. San Bernardino:http://soufangroup.com/tsg-intelbrie...-threat-radar/

Perhaps we will learn one day how the mental health agencies responded to the likely referral; I note the Met gave advice to the family to make contact with them, but it not clear if such a referral was made.