Dzhokhar Tsarnaev coolly dropped off a homemade bomb in the crowd at the Boston Marathon and then walked away amid the confusion as another explosive set by his brother detonated nearby, federal authorities alleged Monday in charging the teen with a terrorist act that could carry the death penalty.
In a criminal complaint unsealed in Boston federal court, prosecutors alleged that Mr. Tsarnaev, a 19-year-old college sophomore, detonated a weapon of mass destruction—a homemade bomb—in an attack that killed three and injured more than 200 on April 15. The complaint offered new details on the young man’s alleged actions during the bombing, as well as the chaotic chase days later that ended in a shootout and the death of his 26-year-old older brother, Tamerlan.
The younger brother has been communicating with Federal Bureau of Investigation interrogators, according to a law-enforcement official, although the value of his written answers to questions wasn’t immediately clear. Mr. Tsarnaev can’t speak due to a gunshot wound to his throat which may have been self-inflicted, officials said.