Tashfeen Malik, who with her husband carried out the massacre in San Bernardino, Calif., passed three background checks by American immigration officials as she moved to the United States from Pakistan. None uncovered what Ms. Malik had made little effort to hide — that she talked openly on social media about her views on violent jihad.
She said she supported it. And she said she wanted to be a part of it.
American law enforcement officials said they recently discovered those old — and previously unreported — postings as they pieced together the lives of Ms. Malik and her husband, Syed Rizwan Farook, trying to understand how they pulled off the deadliest terrorist attack on American soil since Sept. 11, 2001.
Had the authorities found the posts years ago, they might have kept her out of the country. But immigration officials do not routinely review social media as part of their background checks, and there is a debate inside the Department of Homeland Security over whether it is even appropriate to do so.