President Obama vowed Saturday that investigators would "get to the bottom" of the San Bernardino shooting massacre as the FBI investigated links between the shooters and terrorist groups.
One of the assailants, Tashfeen Malik, pledged allegiance to an Islamic State leader in a Facebook posting, officials said. Her husband, Syed Rizwan Farook, had contact with people from at least two terrorist organizations overseas, including the Al Qaeda-affiliated Nusra Front in Syria, a federal law enforcement official said.
On Saturday, several news organizations, including CNN and the Associated Press, said the Islamic State described the couple as "supporters" of the group in an online radio broadcast.
The broadcast declared, "We pray to God to accept them as martyrs" but did not say whether the terror organization played any role in the planning of the San Bernardino attack.
FBI Director James Comey said that the assailants showed signs of "radicalization" but that there was no evidence they were part of a larger terrorist network.
President Obama, in his weekly radio address Saturday, said investigators are still trying to get a "fuller picture" of the shooters' motives.
"It is entirely possible that these two attackers were radicalized to commit this act of terror," the president said. "And if so, it would underscore a threat we've been focused on for years — the danger of people succumbing to violent extremist ideologies."
Obama also renewed his call for tighter controls on guns.
"We know that the killers in San Bernardino used military-style assault weapons — weapons of war — to kill as many people as they could," the president said. "It's another tragic reminder that here in America, it's way too easy for dangerous people to get their hands on a gun.
"For example, right now, people on the no-fly list can walk into a store and buy a gun. That is insane," he said. "If you're too dangerous to board a plane, you're too dangerous, by definition, to buy a gun. And so I'm calling on Congress to close this loophole, now."
Farook and Malik died in a police shootout Wednesday, several hours after bursting into a holiday potluck for the San Bernardino County Health Department and killing 14 people.
Authorities in Pakistan said Friday they were investigating whether Malik had ties to Islamic militant organizations.
Officials cautioned that Malik's Facebook posting did not mean that the militant group directed her and her husband to carry out the attack and that investigators think it instead suggests that the couple had become self-radicalized.
A Facebook spokesman confirmed that the company had taken down the profile page, which included the post cited by law enforcement officials. He said the post was discovered a day after the shooting when Facebook employees conducted a search of the site for the shooters' names.
The company's policy, he said, was to remove posts that "support or glorify" terrorism. The post had gone up about 11 a.m. Wednesday, around the same time the shooting began, he said.
Facebook provided the contents of the post to law enforcement, according to a source familiar with the matter.
Witnesses and police have said Farook, a county public health worker, had been at the holiday party Wednesday but left, possibly after a disagreement with a co-worker, and returned with Malik to attack the gathering.
That could be construed as workplace violence, the law enforcement source said, noting that evidence and witness recollections suggest that they shot Farook's supervisors first. Or, the source said, "after they got away" and were missing for several hours, they might have hoped to launch a previous plan for an even larger strike.
An acquaintance who prayed with Farook at a San Bernardino mosque told The Times that the shooter said he liked his wife because she wore a niqab, a veil that covered almost all of her face.