FBI Arrest Texas Man For Sending Hundreds of Threats Over Five Years

[From article]
According to the complaint, since December 2008, more than 500 hoax letters were mailed from the North Texas area to cities across the U.S. and to U.S. Embassies abroad. The initial letters, sent out on December 4, 2008, had a “Dallas, Texas” postmark and contained a white-powder substance. Law enforcement has identified more than 15 batches of similar letters sent from the Dallas area from December 2008 to the present. The language used in the letters as well as the method of sending the letters, indicate that one person, Truong, is responsible for sending all of the hoax letters. In all but two of the batches of letters, a white-powder substance was included in the envelope.
[. . .]
These letters were sent to pre-schools and elementary schools across the country as well as to Lockheed Martin in Grand Prairie, Texas. HAZMAT responded to the location of many hoax letter recipients, including Mi Escuelita Preschool Crossover in Dallas.
In June 2013, 28 public schools in Boston received letters that resulted in HAZMAT responses. That investigation resulted in the identification of an IP address in Rowlett associated with Truong.

http://www.fbi.gov/dallas/press-releases/2014/rowlett-man-arrested-for-sending-hundreds-of-hoax-white-powder-letters

Rowlett Man Arrested for Sending Hundreds of Hoax White Powder Letters
U.S. Attorney’s Office
July 28, 2014
Northern District of Texas