The brothers were apparently not tied to any Islamic terrorist group.
Two U.S. officials say preliminary evidence from an interrogation suggests the suspects in the Boston Marathon attack were motivated by religion but were apparently not tied to any Islamic terrorist groups.
The two brothers, born in the Chechen region of Russia, practiced Islam.
The U.S. officials spoke today on condition of anonymity because they were not authorized to publicly discuss the investigation.
One of the brothers died in a police shootout Friday. The other brother was formally charged today after being questioned by federal officials in his hospital room where he is recovering from multiple injuries.