Defense
AP
Dzhokhar (left) and Tamerlan (right) both became naturalized U.S. citizens.
The revelation is sure to fuel criticism of the FBI and U.S. counterterrorism protocols.
Tsarnaev, 26, was killed in a police shootout in Watertown, Mass. early Friday while his younger brother Dzhokhar, 19, was captured Friday night and is reportedly speaking with investigators while hospitalized.
The ethnic Chechen brothers are suspected of detonating homemade bombs at the Boston Marathon on April 15, which led to three deaths and more than 260 injuries.
The Associated Press reports that the CIA added Tamerlan to the highly classified "Terrorist Identities Datamart Environment" (TIDE) database as well as the declassified Terrorist Screening Database after the FBI interviewed him about a Russian tip that he had become a "follower of radical Islam and a strong believer."
Authorities told Reuters that the database — which is maintained by the National Counterterrorism Center (NCTC) and contains more than 450,000 people — is so large that investigators do not routinely monitor everyone registered as known, suspected, or potential terrorists.
But fewer than 5 percent of the TIDE entries are U.S. citizens or legal residents, according to the NCTC, which means that the pool to which Tamerlan belonged was relatively small.
As of March 2012 the NCTC can copy and examine entire government databases — including law enforcement investigations, health information, employment history, travel and student records, online activity, and biometric information — to predict possible criminal behavior of any U.S. citizen.
The FBI said they didn't keep tabs on Tamerlan because their initial investigation in 2011 failed to find “any terrorism activity, domestic or foreign” in government databases and on websites that promote extremist views and activities.
But Tamerlan subsequently traveled to Dagestan and Chechnya, became increasingly confrontational in his beliefs, and began posting jihadist videos online.
When he left for Russia in January 2012, his name was also on the a database maintained by the Homeland Security Department's Customs and Border Protection bureau. (He was not put on the "no-fly" list or the Selectee List, which triggers extra security screening at airports.)
However, he had already been automatically downgraded in the border database , so he neither got secondary inspection on his re-entry at New York's JFK Airport nor was he monitored afterward.
"Yes, the system pinged when he was leaving the United States. By the time he returned, all investigations - the matter had been closed," Napolitano told the Senate Judiciary Committee on Tuesday.
Sen. Lindsey Graham (R-S.C.) told Fox News that the FBI missed the Russia trip because Tsarnaev's name was misspelled when he got on the airplane.