Investigators continue to uncover more and more disturbing information about the Tsarnaev brothers, accused of setting off bombs at the Boston Marathon.
A common theme of much of the news involves so-called "radicalization" of young people right here in America.
The Tsarnaev family may have had links to Muslim terrorists in southern Russia.
But it appears the brothers and, in all likelihood, their mother, adopted attitudes that excused and even encouraged violence while they lived here in the United States.
Investigators have talked to a man, once identified only as "Misha," who family members say influenced the Tsarnaev brothers' attitudes concerning Islam.
It turns out he is a Rhode Island resident named Mikhail Allakhverdov, who insists he does not condone violence and, in any event, had not talked with the Tsarnaevs in three years.
If not "Misha," who or what turned the brothers into vicious murderers? Someone else in this country? Someone abroad, communicating via the Internet?
Finding out will be the foundation of the Boston Marathon bombing investigation.
Clearly, two young men who for a time seemed to have no hatred for Americans developed one that made them capable of murder.
Without knowing how that happened, it will be impossible to guard against it occurring again.