A wallet containing the drivers license for Tamerlan Tsarnaev is seen in a still handout image entered as evidence in the trial of Boston Marathon bombing suspect Dzhokhar Tsarnaev provided by the U.S. Attorney's Office in Boston, Massachusetts on March 18, 2015. REUTERS/U.S. Attorney's Office/Handout via Reuters

BOSTON (Reuters) - The older of the two brothers behind the deadly 2013 Boston Marathon bombing passed a test to become a U.S. citizen three months before the attack, the Boston Globe reported on Monday, citing federal documents.

Tamerlan Tsarnaev, a 26-year-old ethnic Chechen who had immigrated to the United States from Russia a decade before the attack, had correctly answered questions about American history and demonstrated proficiency in English. But the U.S. immigration officer who reviewed his test did not immediately approve Tsarnaev’s citizenship application, the newspaper reported.

Its report was based on 651 pages of heavily redacted documents released by the Department of Homeland Security.

Tsarnaev was the older of the two brothers who carried out the April 15, 2013, attack, which killed three people and injured 264, and three days later shot dead a university police officer while they attempted to flee the city. He died following a gunfight with police in the suburb of Watertown, Massachusetts, after this younger brother, Dzhokhar, ran him over in a hijacked sport-utility vehicle.

Dzhokhar Tsarnaev, now 22, was found guilty last year of carrying out the attack and sentenced to death. He is a naturalized U.S. citizen.

The files also contained details on Ibragim Todashev, who was shot dead by law enforcement officers during an interrogation in Florida a month after the attack.

The files showed no signs that federal investigators had regarded Tsarnaev or Todashev as security threats prior to the attack, the Globe reported.

In a related legal matter, court papers unsealed in connection with the case of the friend of the younger Tsarnaev convicted of lying to investigators in connection with a terrorist probe offered new details on what Dzhokhar Tsarnaev told the FBI during an interrogation while he was hospitalized after the gunfight.

Dzhokhar Tsarnaev told investigators that the brothers had not told any of their friends about the planned attack because they trusted no one else and that the younger Tsarnaev had not warned any of his friends to stay away from the marathon that day because he did not care if they got hurt.