Dzhokhar Tsarnaev Says His Brother Planned the Boston Marathon Bombing

Not part of a wider terrorist network

(CNN) -- The surviving suspect in the Boston Marathon bombings has indicated that his older brother, not any international terrorist group, masterminded the deadly attack, a U.S. government source said.

Dzhokhar Tsarnaev, who has been hospitalized with a tube down his throat in recent days, communicated with investigators by writing and nodding.

The preliminary interviews with Tsarnaev suggest the two brothers fit the classification of self-radicalized jihadists, the source said.