FBI investigates letters with ‘unknown substance’ sent to US election officials
(www.theguardian.com)
His name was Bruce Ivins. Charges were filed. He was hounded the same way Aaron Swartz was by Robert Mueller's FBI (he was director at the time).
Later, it was all but proven he was innocent. Essentially the FBI overstated their case and it was extremely unlikely that Ivins could have made anthrax so pure in the lab facilities he had access to.