But there were good reasons that the tip didn’t trigger a more aggressive American investigation, current and former intelligence and law-enforcement officials tell The Daily Beast.

Those officials pointed to the FSB’s habit of treating much behavior by Chechens as suspicious, and nearly all such behavior as terror-related. The Tsarnaev request, they speculated, was likely triggered by the FSB’s concern that he would participate in or provide support to Chechen insurrectionists in Russia, rather that by any sense of a threat to American interests.

“The FSB is mad at a lot of Chechens,” said Michael Hayden, the former director of the CIA and the National Security Agency, who noted that he did not know at this point whether there was enough intelligence to warrant a full-scale investigation into Tsarnaev in 2011. “Not all of them are terrorists, and even fewer of them are dangerous to the United States.”

“When stuff like this happens, we did what we did we called the long pause,” said Hayden. “You get with your staff, you say it’s these two Chechen idiots, you see what’s in the database. You collect so much stuff, then you go and explain it eventually to Congress.”