UPDATE: Dzhokhar Tsarnaev has gained consciousness and is responding, in writing, to investigators' questions.
Investigators are asking about other cell members and other unexploded bombs...
According to this New York Times report, authorities now believe that Boston Bombing suspect No. 2, Dzhokhar Tsarnaev, attempted to commit suicide:
The authorities said Sunday that they believed that Mr. Tsarnaev had tried to kill himself, based on the extent of the gunshot wound to his neck.
The injury “had the appearance of a close range, self-inflicted style,” a senior law enforcement official said. “He’s not in good shape.”