including two more u.s. postal workers and 17 people would become sick after opening or handling letters that contained the deadly anthrax bacteria. after a massive seven-year investigation involving interviews with more than 9,000 people, the fbi finally declared that they knew who did it. >> based on the totality of the evidence we had gathered against him, we are confident that dr. ivans was the only person responsible for these attacks. >> he was a government biodefense researcher and federal prosecutors say they had d.n.a. evidence leading to an anthrax vial in his lab. ivins was never charged with any crime because he killed himself in 2008 and so, what many consider to be the largest fbi investigation in history ended with no conviction. bret? >> bret: kristin, thank you. more on today's arrest with the panel in a bit. in other news, the trump administration is extending an invite to russian president vladimir putin to visit the u.s. early next year. but, after what many saw as