Washington: According to federal law enforcement officials, Tashfeen Malik, who with her husband Syed Rizwan Farook carried out the shooting in San Bernardino on Wednesday, had pledged allegiance to the Islamic State in a Facebook post.
However, there's no evidence the group directed the couple to launch the attacks that killed 14 and wounded 21, said the officials.
We believe the couple were more self-radicalised and inspired by the group than actually told to do the shooting, said officials.
The couple had met online and married two years ago.
The FBI is now treating the San Bernardino shooting as an act of terrorism, an agency official said.
The post had been removed from the social media site.
"The investigation so far has delivered indications of radicalization by the killers and of potential inspiration by foreign terrorist organisations," Xinhua quoted FBI saying.
The couple shot down 14 people Wednesday at a Southern California social services center and injured several. According to local police, "some degree of planning" was involved in the shooting spree.
The two suspects, 28-year-old US citizen Syed Farook and his 27-year-old wife Tashfeen Malik, had 1,600 rifle and 2,000 9-millimeter rounds and 2,500 0.223 rifle rounds at home, as well as 12 pipe bombs and tools to make bombs, according to police.
And those do not include the hundreds of rounds they fired in the shooting and gunfire with police.