They're investigating the suspect wife Katherine Russell.

Katherine Russell, widow of Boston Marathon bombing suspect Tamerlan Tsarnaev. (Photo William Farrington/Polar …A few years ago, in a photo essay for Slate.com, boxer-turned-
Boston-Marathon-Bombing suspect Tamerlan Tsarnaev
said: “I don’t have a single American friend. I don’t understand them." But Tsarnaev, 26, who died Friday in a police shoot-out during a botched getaway, fell in love with and married one: Katherine Russell, a 24-year-old Rhode Island native and the mother of their 3-year-old daughter, Zahara.
The young family lived in a Cambridge apartment that had been leased more than 10 years ago by Tsarnaev's parents. Russell worked 70 to 80 hours, 7 days a week as a home health-care aide, her lawyer, Amato DeLuca, told reporters, and she thought her husband was caring for their toddler at home while she was at work. Instead, he allegedly was planning out the terrorist attack that killed 3 and maimed more than 170 others at the finish line of the Boston Marathon last week.
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