Dzhokhar Tsarnaev is communicating with interrogators and has said that his Islamic faith was motivation for the terrorist attack on the Boston Marathon.

Tsarnaev was officially charged today with conspiring to use a weapon of mass destruction. He suffered a throat injury in his standoff with Boston police leaving him unable to speak. He has been communicating through writing.

A source close to the investigation told the Associated Press that while radical Islam influenced the two brothers, information they have obtained indicates they were not working with a terrorist group. However, the information has not been verified and they are comparing Tsarnaev’s statements with cell phone and email records.

Tsarnaev was charged in U.S. criminal court rather than being designated as an enemy combatant against the demands of several politicians. White House Press Secretary Jay Carney said that because Tsarnaev was a nautralized U.S. citizen, he cannot face a military tribunal under U.S. law.

Information released Monday confirm that two Kazakhstan nationals were arrested on Saturday in the Boston area in connection with the bombing investigation. The two are suspected of immigration violations and are believed to have contact with the brothers.