Three hours before gunmen attacked an anti-Prophet Muhammad event in Garland, Texas on Sunday, the FBI sent a bulletin to local police with a photo of one of the shooters, Elton Simpson, noting that he was "interested in the event," FBI director James Comey said.
At the time, the FBI had no reason to believe that Simpson intended to attack the event, Comey told reporters Thursday. Nor did the agency know that Simpson was already on his way there.
Comey also said that he does not believe that the police officer who shot Simpson and the second gunman, Soofi Nadir, was aware of the bulletin.
He went on to say that while the investigation of the Phoenix gunmen is far from complete, Comey believes the FBI acted appropriately.
The FBI originally investigated Simpson for allegedly planning to join a terror group in Africa five years ago. That case ended last year, when Simpson was convicted of lying to agents about his plans. He faced three years of probation. The FBI saw no signs that Simpson was a threat, Comey said.
But the FBI reopened its investigation of Simpson in March, when he made statements on social media indicating a renewed interest in jihad, this time in connection with ISIS, Comey said.'
Two weeks before the Garland event, which invited artists to draw illustrations of Muhammad, the FBI and Homeland Security warned law enforcement agencies across the country that it was at risk of being targeted by Islamic extremists. The advisory noted that supporters of ISIS and other terror groups had posted links to the contest on Twitter.
Simpson was reading those posts, and communicated with an American in Somalia who'd called for attacking the event, investigators have said.
The FBI then developed information that Simpson might be interested in traveling to Garland, Comey said.
The Sunday bulletin followed.
According to Comey, the Texas plot is a dramatic example of the changing nature of the terror threats.
"Only a few years ago," Comey said, "If someone wanted jihadist propaganda, they would have to go find it on the Internet. So we focused on the places they'd go."
Now he says the ISIS message is being pushed into the pockets of people who are interested in it through social media.
"It's recruiting and tasking at the same time. The old distinction between inspiration and direction is no longer relevant."
Comey said hundreds of people in the U.S. — maybe thousands — "are consuming this poison."
The FBI now has hundreds of investigations of potential home grown extremists under way, with cases open in every state.
"I know there are other Elton Simpsons out there," Comey said.
Finding them, however, is a "very hard task," he said.
Investigators can follow messages that are posted on public twitter accounts. But ISIS recruiters are steering people off Twitter into encrypted forums, which the government cannot see, Comey said.
"Its the old going-dark problem, in living color," said Comey.
He added: "We have hundreds working on it around the clock. But in almost every case of violence, someone saw something. A friend, a family member. Its more important than ever for people to speak up."
The subject of terrorist recruiters "going dark" was the subject of a Senate Homeland Security committee hearing on Thursday.
"When this happens, when they go dark, it's harder to track them," J.M. Berger, a non-resident fellow and expert on U.S. relations with Islamic countries at the Brookings Institution, told senators.
The other issue that complicates tracking terrorists on social media is that companies have become more aggressive in shutting down those types of accounts, Berger said. When accounts are suspended, it's tougher to track the people behind the account.
However, Americans aren't likely to support government monitoring of their social media accounts, given the backlash against the surveillance of phone records.
A federal appeals court ruled against the National Security Agency's bulk collection of telephone call information on Thursday, completely rejecting the government's legal justification for the program.
"The appetite in the country probably isn't open to…the FBI backing up thousands and thousands and thousands of social media accounts," Berger said.
— with Halimah Abdullah and Jon Schuppe