The couple behind the United States attack in San Bernardino, that killed 14 people, did target practice days before, the FBI has said.
Tashfeen Malik and husband Syed Farook visited shooting ranges in the Los Angeles area, said David Bowdich, assistant director of the FBI's Los Angeles office.
He said both were radicalised and had been "for some time".
The US is investigating last week's attack, which happened at a health care centre, as an act of terrorism.
But Mr Bowdich said there was no evidence yet that last week's tragedy, the most deadly terror attack in the US since 9/11, was plotted from overseas.
The FBI did not have an investigation open on restaurant inspector Farook before he and his wife opened fire on his colleagues at a work event at the Inland Regional Center.
They were both killed hours later in a shoot-out with police.
Investigators said they found 19 pipes that could have been turned into bombs at the couple's apartment, rather than the 12 previously reported.
US officials have said that Farook travelled to Saudi Arabia and returned about two weeks later with Malik, who was able to come to the country on a fiancée visa.
Farook's father told Italian newspaper La Stampa his son sympathised with IS and was fixated with Israel.
The family's lawyer said he had recently told them co-workers had mocked his beard, and that the family knew he had two handguns and two rifles.
But they did not know about the arsenal of weapons the couple had amassed.
Malik reportedly praised IS on Facebook on the day of the attacks.
The US Justice Department said on Monday it was monitoring any anti-Muslim sentiments or attacks that may emerge in the wake of the mass shooting.