A couple who killed 14 people in San Bernadino, California had been discussing martyrdom online a yearbefore they met in person and married, the FBI has revealed.
Syed Farook, 28, and Tashfeen Malik, 29, who married each other in 2014 had both been in interested in Islamist-inspired violence before they got to know one another.
A US government source said that Farook may have been plotting an attack as early as 2011.
FBI Director James Comey has said that the pair had been inspired by foreign terrorist organisations and were homegrown violent extremists".
The father of Tashfeen Malik has spoken out condemning his daughter's actions over the killings.
Speaking to the Associated Press from Jeddah, Saudi Arabia, by telephone Gulzar Ahmad Malik spoke of his sadness.
Comey emphasised how critical it was to know if the marriage between Farook and Malik had been arranged by a militant group as a way of carrying out attacks in the US.
However he indicated that there was no evidence yet to suggest that.
21 people were also injured in the attack on an office Christmas party in San Bernadino.