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According to a congressional report prepared for the House Homeland Security Committee, and reviewed by NBC News, the Russian government warned American authorities about Tamerlan Tsarnaev more than a year and a half before he participated in the Boston Marathon bombings last April.

A series of missed cues and clerical errors led authorities to miss several opportunities to detain Tsarnaev as he traveled between the U.S. and Dagestan. At one point:

Tsarnaev was supposed to be pulled aside for questioning at JFK airport because he was considered potentially armed and dangerous, but he slipped through undetected because someone had misspelled his last name in a security database.

The FBI opened an investigation of Tsarnaev in 2011, but it did not meet standards necessary to allow for surveillance. His name was put on a “Hot List” that would trigger an alert whenever he entered or left the country.

The name was misspelled “Tsarnayev,” and on one instance when the alert was triggered, Tsarnaev was just one of nearly 100 Hot List names going through JFK airport that day. He was not deemed high priority and not pulled aside.

The document also links the older Tsarnaev to the murders of three individuals found with their throats cut in September 2011 in Waltham, Mass. Tsarnaev’s possible connection to the murders was first reported by BuzzFeed six days after the bombing. An associate of Tsarnaev who was shot and killed by an FBI agent in the wake of the bombings was supposedly about to sign a statement implicating both of them in the triple homicide.

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