CNN) -- Boston Marathon bombing suspect Dzhokhar Tsarnaev has told investigators his older brother Tamerlan was the driving force behind last week's attack and that no international terrorist groups were behind them, a U.S. government source said Monday.
Preliminary interviews with Dzhokhar Tsarnaev indicate the two brothers fit the classification of self-radicalized jihadists, the source said. Dzhokhar Tsarnaev, wounded and held in a Boston hospital, said his brother wanted to defend Islam from attack, according to the source.
The government source cautioned that the interviews were preliminary, and that Tsarnaev's account needs to be checked out and followed up on by investigators.
Dzhokhar Tsarnaev has been charged with using and conspiring to use a weapon of mass destruction resulting in death, and one count of malicious destruction of property by means of an explosive device resulting in death, the Justice Department announced Monday. The 19-year-old was "alert, mentally competent and lucid," U.S. Magistrate Judge Marianne Bowler found during the brief initial court appearance that took place in Tsarnaev's hospital room.
