investigators have taken dna samples and other items from katharine russell at her parents' home in rhode island. they will compare the samples to female dna found on a fragment of one of the pressure cooker bombs used in the boston attack. federal agents, by the way, also trying to determine if there's a link between tamerlan and this man, william plotnikov, a canadian boxer turned jihadist killed a year ago in a shoot-out with russian troops. firefight happened in the same region tamerlan was visiting. he returned to the u.s. quickly thereafter. we have reporters covering all angles of the investigation. and we're staying on top of this story. meanwhile, a defiant president obama says the u.s. won't be intimidated by bombings in boston. in a news conference over at the white house just a little while ago the president was asked whether people should be afraid of attending large gatherings after the attack at the boston marathon, and he said, absolutely not. >> we're not going to stop living our lives because warped individuals try to intimidate us. we're going to do what we do which is

katharine russell tsarnaev last saw her husband just hours before he was killed in a fire fight with police. now she's holed up at her parents' house 90 miles north of husband was and according to involved in something like this. >> the reports about her husband and brother-in-law came as an absolute shock. >> reporter: now hounded by the media, the 24-year-old home health aid is trying to find answers to the questions the rest of the world is about the man she married in 2010, the daughter of her 3-year-old daughter. >> they are trying to come to terms with the struggles and deep threats. >> reporter: raised a christian she met tsarnaev at a nightclub in 2007. at the time shea was a communications student. she dropped out of school and married tamerlan. he was often violent with katharine and wasn't arrested for assaulting her in 2009. katharine and her two sisters grew up on a quiet cul-de-sac in roye. her mother, a nurse and her father an emergency room doctor. >> i've seen the baby. she looked like aing to ler age. a couple of times. just playing in the yard. thinks like that. >>