BOSTON (CBS) – New documents just released are providing a glimpse into the minds of the Tsarnaev brothers before and after the Boston Marathon bombings.

The FBI released new documents Monday related to the questioning they conducted of one of the bombers. They’re heavily redacted, but still give us information about who knew what about the Marathon bombings.

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Documents filed in the appeal of Dzhokhar Tsarnaev‘s friend Robel Phillipos include some notes on the convicted terrorist’s first conversations with the FBI. It all happened in the days following the arrest of Dzhokhar while he was being treated at Beth Israel Deaconess Medical Center.

Read: Phillipos Documents (part 1 .pdf)

Read: Phillipos Documents (part 2 .pdf)

It had been a week of terror and grief in Boston. Two deadly explosions at the Marathon finish line and a manhunt for the bombers. Tamerlan Tsarnaev was killed, his younger brother Jahar was arrested and rushed to the hospital.

The FBI was desperate to know if anyone else was involved, and whether there were more bombings to come. But according to the documents, Dzhokhar told the FBI that no one else took part in the plan because “they could not trust anyone else.”

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He also told them, “There were no other attacks planned, there were no unaccounted devices.”

According to the documents, the younger Tsarnaev also described how the brothers moved down Boylston Street and that “no one helped them identify or select possible locations to attack.”

He also indicated that “each of them decided on their own where they would stop near the finish line” to drop their explosives.

A second batch of documents obtained by the Boston Globe gives us new information about Tamerlan and his friend Ibragim Todashev, and show that just three months before the bombings he passed a US citizenship test, pledging allegiance to the United States and denying any links to terrorism.

Some people question why red flags didn’t go up as Tamerlan applied for citizenship because he had recently traveled overseas and had an arrest record for assault. But the federal Immigration Services says no errors were found in Tsarnaev’s processing.

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