Tashfeen Malik pledged allegiance to the leader of ISIS just before she and her husband carried out the San Bernardino massacre, law enforcement sources told NBC News.
Malik posted a statement of support for Abu Bakr al-Baghdadi on Facebook "just before the attack," one official familiar with the issue said.
And now investigators are looking into whether the Pakistan-born Malik radicalized her husband, Syed Rizwan Farook.
The revelation came just hours after Farook's brother-in-law insisted the slain suspect was an observant Muslim but not a "radical" and never gave any indication of what may have motivated him and his wife to attack the city's Inland Regional Center with four guns and explosives.
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Farook, 28, and Malik, 27, were killed in a shootout with police a few miles away — and more than four hours — after the bloodbath in San Bernardino. They had left their 6-month-old daughter with Farook's mom before they went off to commit mass murder, police said.
While the FBI still has not said whether the deadly attack that left 14 dead and 21 wounded was motivated by Islamic terrorism, NBC News reported Thursday that Farook appeared to have been radicalized and had been in touch with people in the Los Angeles area who expressed support for jihad. Intelligence sources said he appeared to have been in communication with people overseas who are of interest to U.S. authorities.
Farook met his future wife online and married her in 2013 while on a pilgrimage to Mecca, NBC reported Thursday. But Malik entered the U.S. on a K-1 visa, which is required of a fiance engaged to a U.S. citizen. These visas are granted after the applicant undergoes a rigorous security screening process aimed as preventing so-called "Green Card" marriages.
Relatives have described Farook and Malik as a happy couple who gave no outward sign of being Islamic fanatics. They even registered at Target before their baby daughter was born.
But in the aftermath of the massacre, police discovered the couple had amassed an arsenal in their rented Redlands, California home.This is a breaking news story. Please refresh for updates. Corky Siemaszko contributed. This article originally appeared on NBCNews.com.