Scene of Boston marathon bombings
Scene of Boston marathon bombingsReuters

US officials knew about the potential danger of Boston Marathon bomber Tamerlan Tsarnaev, according to a soon-to-be-released Congressional report - but a spelling error led them to miss his frequent flights out to Dagestan for terror training. 

Russian officials warned the US that Tsarnaev was armed and dangerous as much as a year and a half before the April 2013 bombingNBC News reports Wednesday. But Tsarnaev's name was misspelled in a security database, leading authorities to miss him completely. 

In March 2011, Russian intelligence agency FSB notified the FBI with concerns about Tamerlan Tsarnaev and the Tsarnaev family, which had emigrated to Massachusetts nearly ten years earlier. In the letter, FSB included contact information, with addresses and phone numbers, for many of the members of the Tsarnaev family, including Tamerlan and his mother, and warned that Tamerlan was gaining a reputation for associating with violent Islamists

That same month, the FBI recruited the Boston Joint Terrorism Task Force, a multiagency anti-terrorism group, to open an investigation into Tamerlan Tsarnaev. An FBI member from the Force interviewed Tsarnaev, but no surveillance was conducted; another member then entered a memo about Tsarnaev into a Customs and Border Protection database called TECS, putting Tsarnaev on a "Hot List" every time he left or entered the US. 

However, just four months later, the investigation was closed. According to the June 2011 report, “the assessment found no links to terrorism.”

US authorities missed the mark yet again in September 2011, after three Jewish men linked to Tsarnaev were found murdered in Waltham, Mass. Two years later, Tsarnaev's associate, Ibragim Todashev told the FBI about the Waltham murders - but Tsarnaev himself was not questioned in the aftermath of the killings. 

A US intelligence official confirmed to NBC News that the US missed yet another opportunity to catch Tsarnaev, however; this time, when the FSB contacted the CIA, shortly after the Waltham murders. The FBI allegedly did not reopen the case, despite the second warning. 

On Oct. 19, 2011, the CIA shared information on Tsarnaev with the National Counterterrorism Center (NCTC), DHS, the State Department and the FBI. The information shared included two possible dates of birth, his name and a possible alternate spelling of his name. The CIA then nominated Tsarnaev for inclusion on the terrorism watch list - the massive Terrorist Identities Datamart Environment (TIDE) database - and it was. But there was one fatal error: the entry reads "Tsarnayev" instead of Tsarnaev. 

The note directs that if Tsarnaev is encountered leaving or reentering the U.S., his detention is “mandatory.” It says, “Escort to CBP [Customs] secondary and detain.”

“Detain isolated and immediately call the lookout duty officer at NTC (24X7),” says the note. “Call is mandatory whether or not the officer believes there is an exact match. Advise the person answering the phone that you have a code tip lookout intercept.”

But, according to the daily, the US failed to heed that warning at least once. On January 21, 2012, Tsarnaev boarded a flight from JFK airport in New York to Moscow despite the alert. Sources familiar with the report claim that he was just one person in a sea of over 100 "Hot List" travelers that day and was passed over as not being high priority. 

In July, after returning from six months of Jihad training in Dagestan, Tsarnaev landed again in JFK. Once again, authorities failed to heed the alert warning because of the misspelling. Tsarnaev was not apprehended until he was shot and killed by police in a gunfight shortly after the Boston Marathon bombings, in April 2013. 

The House Homeland Security Committee, which is chaired by Rep. Michael McCaul (R.-Texas), is expected to make its report public as early as Thursday.