Female shooter Tashfeen Malik pledged allegiance to Islamic State in Facebook post on day of San Bernardino massacre
One of the two people accused of killing 14 at a holiday party in California posted an online statement pledging allegiance to a leader of the Islamic State militant group.
Tashfeen Malik, 27, and her husband, Syed Rizwan Farook, 28, were killed in a shootout with police hours after Wednesday's massacre at a social services agency in San Bernardino, east of Los Angeles.
The attack was the deadliest mass shooting the United States has experienced in three years.
Malik, a Pakistani native who had been living in Saudi Arabia when she married Farook, posted an online statement of support for a leader of Islamic State on an account using a name other than her own, CNN reported on Friday, citing US officials.
The attack in San Bernardino appeared to be inspired by - but not directed by - the militant group.
Authorities are investigating whether Malik radicalised her husband. Photo: ABC News
Syed Farook, one of two people involved in the mass shooting. Picture: California Department of Motor Vehicles/TNS
The investigation has been focused on the motivation for the attack, with officials including President Barack Obama and San Bernardino Police Chief Jarrod Burguan saying it may have been motivated by extremist ideology.
The couple left behind a six-month-old daughter.
The attack was the deadliest mass shooting the United States has experienced in three years. Photo: AFP
Twenty-one people were wounded in the attack, the worst gun violence in the nation since the December 2012 shooting at Sandy Hook Elementary School in Newtown, Connecticut.
Farook, a US citizen born in Illinois, was the son of Pakistani immigrants, said Hussam Ayloush, head of the Los Angeles area chapter of the Muslim advocacy group Council on American-Islamic Relations.
Christian Nwadike, who worked with Farook for five years, told CBS his co-worker had been different since he returned from Saudi Arabia.
"I think he married a terrorist," Nwadike said.
Investigators are reviewing the couple's computers and mobile phones to see if they had browsed jihadist websites or had contact with militant groups, according to officials in Washington familiar with the investigation.
Tashfeen Malik, 27, pledged her allegiance to the leader of the Islamic State group, Abu Bakr al-Baghdadi (pictured) on Facebook on the day of the shooting. Photo: AP
The FBI is investigating this week's massacre in California as an "act of terrorism".
They said the finding of Malik's pledge to IS, if confirmed, could be a "game changer" in the investigation, though another source cautioned there was no indication that there was no evidence Islamic State "even knew" who the shooters were.
"Based on the information and the facts as we know them, we are now investigating these horrific acts as an act of terrorism," David Bowdich, assistant director of the Federal Bureau of Investigation's Los Angeles office, told reporters. Investigators have determined that the Malik and Farook engaged in "extensive planning" before the attack, he said.
